US3506438A - Method of producing beryllium composites by liquid phase sintering - Google Patents

Description

April 14, 1970 R. H. KROCK ET AL 3,506,438

METHOD (1F PRODUCING BERYLLIUM COMPOSITES BY LIQUID PHASE SIN'I'ERING Filed July 24, 1967 4 Sheets-Sheet 1 ALUMINUM BERYLLIUM PHASE DIAGRAM WEIGHT PER CENT BERYLLIUM IO I5 3o 5o 8090 I I I l l I J I I l TEMPERATURE C Al+ Be 0 IO 20 3O 4O 5O 6O 7O 8O I00 AI Be ATOMIC PER CENT BERYLLIUM FIG 11 INVENTORS RICHARD H. KROCK CLINTFORD R. JONES BY 6 ATTORN Y April 14; 1970 R. H. KROCK ET 3,506,438

METHOD OF PRODUCING BERYLLIUM COMPOSITES BY LIQUID PHASE SINTERING Filed July 24. 1967 4 Sheets-Sheet 2 INVENTORS RICHARD H. KROCK BYCLINTFORD R. JONES ATTORNEY April 14, 1970 Filed July 24,- 1967 TEMPERATURE. c

SI LVER- BERYLLIUM PHASE DIAGRAM WEIGHT PER CENT BER YLLIUM 4 5 IO I5 20 3O 40 6090 0 IO 20 so 40 so so 10 so 90 I00 nomc PERCENT BERYLLIUM Be INVENTORS RICHARD H. KROCK CLINTFORD R. JONES ATTO RNEY- April 14, 1970 KROCK ET AL 3,506,438

METHOD OF PRODUCING BERYLLIUM COMPOSITES BY LIQUID PHASE SINTERING Filed July 24, 1967 4 Sheets-Sheet 4- INVENTORS RCHARD H. KROCK CLINTFORD R. JONES BY M ATTORAEY United States Patent Int. Cl. B22f 7/00 US. Cl. 75-208 22 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to prime composites of particles of beryllium in a deformable metal matrix and methods of providing such composites through liquid phase sintering. Beryllium powder is mixed with powder of deformable metal constituents and of a minor quantity of fiuxing agent selected from the group consisting of alkali and alkaline earth metal halogenides as the essential ingredients of the resulting powdered mixture. The beryllium powder constitutes about 50% to 90%, by weight, of the powdered mixture. The fiuxing agent may be powder of lithium fluoride or a powdered mixture of lithium fluoride and lithium chloride, in an amount constituting from about 0.5% to 2.0% by weight, of all of the metal additions to the beryllium. The ratio of the amounts of the ingredients of the'lithium fluoride-lithium chloride fluxing agent may vary but preferably is about 1:1. The deformable metal constituent may be either aluminum; or silver; or alloys of aluminum, or of silver or of both. Specifically, the deformable metal constituent may be Al, or Ag, or an alloy of Al-Ag, or an alloy of Ag-Cu, or an alloy of Al-Mg. The powdered mixture is compacted and the resulting green compact is sintered in a non-oxidizing environment, such as argon, at a temperature between about 800 C. and about 1250 C. to substantial elimination of the fiuxing agent content by vaporization.

This application is a continuation-in-part of our copending application Ser. No. 526,746, filed Feb. 11, 1966, and of our copending application Ser. No. 533,156, filed Mar. 10, 1966, now abandoned.

Liquid phase sintering differs from the several other types of sintering techniques in that the sintering of the compact is carried out in the presence of a liquid phase. Liquid phase sinterin-g encompasses raising the temperature of the compressed powder metal constituents to a temperature wherein a predetermined amount of the liquid phase appears. In the liquid phase, one of the metal constituents, the solid, is progressively dissolved in the other metal constituent, the liquid. However, the quantities of these constituents are such that, at equilibrium, some solid phase always exists. It is thought that the liquid wets the solid so as to bring about favorable surface energies existing between the liquid and the solid thereby permitting solution into the liquid phase.

However, heretofore, when beryllium-deformable metal composites were developed in accordance with known ice liquid phase sintering techniques, it was found that the solid, beryllium expelled the liquid, beryllium-deformable metal alloy from the compact during liquid phase sintering. It is thought that the unfavorable surface energy equilibrium causing expulsion of the liquid is due to a tough, tenacious film of beryllium oxide which is present on each particle of beryllium.

The present invention prevents the expulsion of the liquid from the specimen by using an agency to intervene in the sintering stage. The agency either breaks down the oxide film on the beryllium or segregates to the metal oxide interface and lowers the surface energy of the liquid metal with respect to the beryllium oxide film so that the liquid metal progressively dissolves the solid metal during liquid phase sintering.

The agency can be called a fiuxing agent or flux, however, the agent has other characteristics which assist in wetting beryllium so as to surround the beryllium with a ductile envelope phase of a deformable metal-beryllium alloy matrix metal thereby avoiding the expulsion of the liquid from the specimen.

Beryllium has several desirable physical features which make it attractive for a variety of applications such as lightweight gears, lightweight fasteners, airplane parts, aerospace .parts, electronic components and the like. Beryllium metal is lighter than aluminum metal, has a melting temperature that is about twice that of aluminum, will not vaporize appreciably in a vacuum and has a high elastic modulus. However, beryllium has one major drawback which has seriously limited its commercial acceptance, that is, beryllium is inherently brittle at room temperature.

The lack of ductility of beryllium is attributed to the crystal structure of beryllium which is hexagonally close packed. During deformation, the basal planes of the hexagonal close packed structure, being the easiest to slip, are aligned along the working direction. Since slip is crystallographically difficult perpendicular to the basal plane, the ductility of beryllium perpendicular to the primary fabrication direction is practically nonexistent.

Several tentative solutions have been advanced in an attempt to make beryllium metal sufiiciently ductile so as to permit a widespread commercial acceptance of the metal. Cross-rolling and cross-forging have been suggested as fabrication methods which might enhance the ductility of beryllium. These fabrication techniques reduced the number of basal planes along the direction of rolling and resulted in an improved ductility. However, the degree of improvement was far from satisfactory. The fact remained that beryllium must be classified as brittle at room temperature even utilizing the aforementioned method when ductility perpendicular to the fabrication temperature is considered. In addition, the abovementioned technique would not be feasible where the fabrication is, by nature, solely along one axis such as swaging, drawing, and extrusion.

In recent years, attention has been directed to the fabrication of beryllium alloys not having the inherent brittleness of beryllium itself but possessing various outstanding properties of the metal such as, for example, low density combined with high strength. It is thought that US. Patent 3,082,521 fabricated the first ductile beryllium alloy by rapidly quenching the part from a temperature at which it was liquid. However, the beryllium content was not in excess of 86.3 atomic percent which s approximately 30 weight percent. Although the berylium alloy was ductile, the density of the alloy was in ex- :ess of that of aluminum and about equal to that of ti- .anium.

It has also been suggested that beryllium alloys might 9e fabricated by pressing and sintering a mix of metal powders. However, such a method results in expulsion of he matrix metal or metals from the beryllium specimen 1nd the eventual freezing of the matrix metal or metals Lnto globs on the surface of the solid specimen. It is :hought that the expulsion of the matrix metal or metals ls due to the surface energies of the solid beryllium and .he various liquids formed. The unfavorable surface en :rgy equilibrium is believed to be due to a tough, tena- :ious film of beryllium oxide which is present on each particle of beryllium.

A means and method have been discovered for preparing a composite of beryllium and a deformable matrix metal containing from about 50 to 90 percent, by weight, of beryllium thereby producing a composite having a density about the same as or less than that of aluminum, having high strength, and having good ductility. The de- Eormable metal may be either aluminum or silver or alloys wherein aluminum or silver or both are included therein. The ductility is due to the resulting microstructure of the composite. By surrounding the beryllium particles with a ductile envelope phase, a composite is formed where, under load, the beryllium is so constrained by the ductile phase that it and the ductile phase deform continuously.

The 90 percent, by weight, beryllium composite showed a considerable amount of particle contiguity and would represent, it is thought, an upper limit on the percent by weight of the beryllium contained by the composite. A decrease in beryllium content below 50 percent would raise, it is thought, the density value of the composite to a value of little interest.

Alkali and alkaline earth halogenide agents such as lithium fluoride, lithium fluoride-lithium chloride and the like in a determined ratio are utilized to segregate to the solid interface of the beryllium particle and either break down the film on the particle of beryllium and/or alter the liquid-solid surface energy in the system.

Therefore, it is an object of the present invention to provide an agent to promote liquid phase sintering of a mixture of beryllium plus another metal or metal alloys.

A further object of the present invention is to provide a ductile beryllium composite having a low density and high strength.

Yet a further object of the present invention is to provide a ductile composite of beryllium in which beryllium is the predominant ingredient.

Another object of the present invention is to provide a means and method of producing a ductile composite of beryllium and a deformable matrix metal whose microstructure consists of beryllium particles surrounded by a ductile envelope phase of a beryllium alloy matrix metal.

Yet another object of the present invention is to provide a ductile composite of beryllium containing 50 percent, by weight, or more of beryllium.

Yet still another object of the present invention is to provide a ductile composite of beryllium containing about 70 percent, by weight, beryllium, and the remainder a deformable metal selected from the group consisting of aluminum and silver or alloys containing silver or aluminum or both.

A further object of the present invention is to provide an agent which eliminates the expulsion of a deformable matrix metal from a beryllium specimen.

Still another object of the present invention is to provide alkali and alkaline earth halogenide agents used in the fabrication of a beryllium composite.

Another object of the present invention is to provide'a composite of beryllium plus a metal selected from the group consisting of aluminum and silver or alloys thereof that may be sintered to substantially theoretical densit ir'et another object of the present invention is to provide a means and method whereby a ductile beryllium composite may be successfully fabricated in both a practical and economical manner.

A further object of the present invention is to provide an agent selected from the group consisting of lithium fluoride-lithium chloride and lithium fluoride for promoting liquid phase sintering in a mixture of beryllium and a deformable metal, and in which the constituents are used in a predetermined ratio.

The present invention, in another of its aspects, relates to novel features of the instrumentalities of the invention described herein for teaching the principal object of the invention and to the novel principles employed in the instrumentalities whether or not these features and principles may be used in the said object and/or in the said field.

With the aforementioned objects enumerated, other objects will be apparent to those persons possessing ordinary skill in the art. Other objects will appear in the following description and appended claims. The invention resides in the novel combination of elements and in the means and method of achieving the combination as hereinafter described and more particularly as defined in the appended claims.

In the drawings:

FIGURE 1 is a phase diagram for binary alloys of beryllium and aluminum.

FIGURE 2 is a photomicrograph of a beryllium specimen illustrating a matrix metal expelled from the specimen by the forces of surface energy of solid beryllium and various liquids formed.

FIGURE 3 is a photomicrograph of a 30* percent, by weight, aluminum in beryllium composite illustrating the structure of said composite after sintering at 1000" C. for 1 hour.

FIGURE 4 is a photomicrograph. of a 3-0 percent, by weight, aluminum in beryllium composite illustrating the structure of said composite after two represses at 40,000 p.s.i. each followed by an intermediate sinter at 1000 C.

FIGURE 5 is a phase diagram for binary alloys of beryllium and silver.

FIGURE 6 is a photomicrograph of a beryllium specimen of a 25 percent, by weight, silver in beryllium composite illustrating a delta or a gamma intermediate phase surrounding the beryllium particles.

FIGURE 7 is a photomicrograph of a 25 percent, by weight, silver in beryllium composite illustrating the absence of the, delta or the gamma intermediate phase.

Generally speaking, the means and method of the present invention relate to a ductile beryllium composite fabricated by liquid phase sintering. The composite contains from about 50 to percent, by weight, of beryllium, and the remainder an alloy of beryllium containing a deformable metal constituent.

The method of producing the beryllium composite wherein the particles of beryllium are in a deformable metal matrix by liquid phase sintering comprises the steps of mixing predetermined portions of powder beryllium and an amount of powder of a deformable metal constituent together with a minor quantity of a fiuxing agent selected from the group consisting of alkali and alkaline earth halogenides to form a powdered mixture. The mixture is confined and pressed in a die to form a green compact. The compact is then heated in a nonoxidizing environment to a sintering temperature below the melting point temperature of the beryllium and above the beryllium and deformable metal constituent eutectic melting point temperature to produce a composite of beryllium particles surrounded by a deformable envelope of matrix metal. The fluxing agent provides, during the sintering of the compact, a favorable surface energy equilibrium between the particles of beryllium and the melted deformable metal constituent whereby expulsion of the deformable metal constituent from the composite is prevented. It was found that substantially all of the agent is eventually eliminated from the compact during the sintering thereof.

In carrying out the present invention, a beryllium base compact is fabricated by any suitable means such as powder metallurgy techniques. A suggested method utilizing this technique is to mix beryllium powder with a powdered deformable metal constituent and an agent selected from the alkali or alkaline earth halogenides such as lithium fluoride or equal parts of lithium fluoride-lithium chloride. The powders are blended and mixed by ball milling the metal powders and the flux agent with ceramic balls. The blended and mixed powders are compacted to form a green compact by accepted metallurgical methods such as by compacting within the confines of a die or a hydraulic or an automatic press or by placing the powders in a rubber or a plastic mold and compacting in a hydrostatic press. The green compact is sintered in a non-oxidizing atmosphere such as argon or the like at a temperature which may be in the preferred range of about 800 C. to about 1250 C. The sintering temperature utilized is below the 1277 C. melting point temperature of the beryllium but above the beryllium and deformable metal constituent eutectic melting point temperature. The deformable metal constituent will dissolve smaller beryllium particles and will dissove the surfaces of the larger beryllium powder particles thereby surrounding the remaining beryllium particles with a ductile envelope phase of a beryllium-deformable matrix metal. In predetermining the lower limit of the sintering temperature range for the production, by the present method, of any particular beryllium composite, the following facts should be kept in mind. The melting point or liquidus temperatures of the following deformable metal constituents respectively are: aluminum, 660 C.; silver, 960u8 C.; aluminum-silver alloy, 620 C.; silver-copper alloy, 779 C.; and aluminum-magnesium alloy, 450 C.

The agent, lithium fluoride, or the agent, lithium fluoride-lithium chloride, either breaks down the oxide film on the beryllium or segregates to the metal oxide interface lowering the surface energy of the liquid metal with respect to the beryllium oxide film. Simply, the agent causes the liquid to wet the beryllium.

Composites containing about 50 to 90 percent, by weight, of beryllium, and the remainder a deformable metal constituent were successfully fabricated. The deformable metal may be either aluminum or silver or alloys wherein aluminum or silver or both are included therein. The agent prevented the expulsion of the liquid beryllium alloy from the compact by the forces of surface energy, that is, preventing the formation of very fine rounded droplets of the beryllium alloy on the surface of the beryllium specimen. FIGURE 2 shows a beryllium specimen having on the surface thereof an expelled alloy 21 of beryllium. Specimens from which the beryllium alloy has been expelled have gross porosity and as a result are weak, brittle and of little commercial value.

The preferred composition of the agent, lithium fluoride-lithium chloride, utilized is about 50 parts, by weight, of lithium fluoride to about 50 parts, by weight, of lithium chloride. The agent provides an action, such that, upon heating or sintering of the pressed powder mix to the temperature at which the liquid phase forms, expulsion of the melt from the specimen is eliminated. Furthermore, it was found that solution of the beryllium into the deformable metal constituent was enhanced as evidenced by the rounded particles of beryllium in the microstructure.

It was found that the amount by weight of lithium fluoride or of lithium fluoride-lithium chloride agent should exceed 0.5 percent, by weight, of the total of all metal additions. It would appear that the optimum range of the agent is from about 0.5 percent to about 1.0 percent, by weight, of the total of all metal additions. It is believed that the quantity of the agent required is related to the amount necessary to cover the total beryllium surface area. Hence, the minimum amount of agent needed would be a function of the surface area of the beryllium powder. The preferred ratio of the agent lithium fluoridelithium chloride is about a one to one ratio by weight. The utilization of lithium fluoride-lithium chloride agent in other than equal parts or the utilization of both agents in amounts up to about 2.0 percent by weight of all the metal additions produced satisfactory results. It is thought, however, that an equal parts mixture of the lithium fluoride-lithium chloride and 0.5 to 1.0 percent by Weight of all the metal additions of both of the agents achieves optimum results.

It was found that substantially 100 percent of the fluxing agent was lost during sintering. This result would seem to indicate that the flux entered into a chemical reaction whereon it decomposed and then volatilized and/or the flux volatilized as lithium fluoride in the case of the lithium fluoride flux or as lithium fluoride-lithium chloride in the case of the lithium fluoride-lithium chloride flux. In any regard, the flux agent was found to be absent from the composite.

By using the methods of the present invention and the lithium fluoride-lithium chloride agent, composites were fabricated containing from about 50 to percent, by weight, of beryllium without the use of pressure during sintering. Beryllium-aluminum composites were sintered to between about 76.5 and 89 percent of theoretical density by a single sinter and 96 percent of theoretical density by a double repress and an intermediate re-liquid phase sinter and had a density of about 1.94 grams per cubic centimeter. Beryllium-silver composites were sintered to between about and 99 percent of theoretical density and had a density of between 2.19 and 2.29 grams per cubic centimeter. The good strength and low density characteristics of the beryllium were retained and the resulting beryllium composites possessed good ductility. Thus, by substantially surrounding the beryllium particles with a ductile envelope phase of deformable metal-beryllium alloy matrix metal, the beryllium and the matrix metal deform continuously under load.

The beryllium-aluminum phase diagram of FIGURE 1 illustrates that when a beryllium-aluminum mixture containing 70 percent, by weight, beryllium and 30 percent, by weight, aluminum is heated, a liquid forms at 645 C. containing 1 /2 weight percent beryllium, balance aluminum in equilibrium with solid beryllium. Sintering at a higher temperature results in solid beryllium in equilibrium with a liquid richer in beryllium. For. example, at 800 C. the liquid would contain about 2 /2 percent, by weight, beryllium, at 1000 C. about 9 percent, by weight, beryllium, at 1100 C. about 20 percent, by weight, beryllium. Hence, for a 70 percent, by weight, beryllium mixture, the volume percent liquid present at the sintering temperature and the composition of the liquid is a function of the sintering temperature. Very rapid cooling, such as, for example, quenching, from the sintering temperature would preserve the phase relations that existed at the sintering temperature while equilibrium cooling results in a 70 percent, by weight, beryllium of a duplex microstructure at room temperature consisting of 70 percent, by weight, beryllium as solid beryllium particles dispersed in a matrix of 30' percent, by weight, pure aluminum. The volume percentages of liquid and solid present at the sintering temperatures of 800, 1000' and 1100 C. for

various beryllium and aluminum mixtures are given in :he folowing table.

PHASE RELATIONSHIPS IN A BERYLLIUM-ALUMINUM SYSTEM Percent by Percent by Percent by Composite Sintermg Initial weight volume volume density, temp. composition liquid liquid solid gins/cc.

800 C 50 Be 50 AL... 51. 3 41. 59. 0 2. 18

60 Be-4O Al... 41. 0 30. 5 69. 5 2. 09 70 Bra-30 AL... 30. 8 22. 5 77. 5 2. 02 80 Bra- AL... 20. 5 13. 5 86. 5 1. 94 90 Be-lO AL... 10. 2 7. 0 93. 0 1. 88 1,000 O 50 Be-50 AL... 54. 5 45. 0 55. 0 2. 18 60 Be-40 AL... 43. 5 34.0 66. 0 2. 09 70 Be-30 AL... 32. 6 25.0 75. 0 2. 02 80 Be-20 AL... 21. 7 15. 0 85. 0 l. 94 90 139-10 Al... 10. 9 7. 5 92.5 1. 88 1,l00 C 50 Be-50 AL... 62. 5 56. 0 44. 0 2. 18 60 Be-40 AL... 50. 0 42. 0 58. 0 2. 09 70 Be-30 A 37. 5 31. 0 69. 0 2. 02 80 136-20 Al... 25. 0 19. 0 81. 0 1. 94 90 Bis-10 AL... 12. 5 9. 0 91. 0 l. 88

It will be noted that the density values of the composites fall between the density of beryllium and the density of aluminum. The resulting composite containing from about 70 percent, by weight, of beryllium may be sintered to about 76.5 percent of density by a single sinter. Composites containing about 70 percent, by weight, of beryllium require a double repress at 40,000 pounds per square inch and an intermediate re-liquid phase sinter at 1000" C. to attain about 96 percent of theoretical density.

Attention is directed to FIGURE 3, wherein a photomicrograph of 500 magnifications shows an alloy of 30 percent, by weight, aluminum in beryllium composite after being etched by any suitable caching means such as a dilute solution of ammonia hydroxide and hydrogen peroxide. The areas 10 are sintered beryllium particles. The area 11 is the ductile pure aluminum matrix which surrounds the beryllium particles. The compact was sintered for 1 hour in an argon atmosphere at 1000 C. and had a density of about 1.80 grams per cubic centimeter which was about 89% of the theoretical density.

FIGURE 4 shows the structure of an alloy of 30 percent, by weight, aluminum in beryllium composite that has been subjected to two represses at about 40,000 p.s.i. followed by an intermediate sinter at 1000 C. The density is about 1.94 grams per cubic centimeter which is approximately 95.2% of the theoretical density.

The beryllium-silver phase diagram of FIGURE 5 illustrates that beryllium-silver mixtures having beryllium content in excess of about 2.3 percent, by weight, form a melt and are in equilibrium with substantially pure beryllium at temperatures above about 1010 C. The composition of the silver-beryllium alloy melt is determined by the temperature of the melt and is independent of the percent, by weight, of beryllium while the relative amount of the solid beryllium and of the matrix metal at the sintering temperature is determined by the temperature itself, as well as by the percent, by weight, of beryllium relative to the percent, by weight, of silver. Berylliumsilver mixtures have been sintered at a plurality of temperatures between 1050 C. and 1250" C. Liquid phase structures have been obtained at each of the temperatures at which the compact was sintered. It was noted that when the percent, by volume of the liquid is less than about 5 percent, the sintering in the liquid phase is slow and porosity is apparent in the materials. It was also noted that when the percent of volume of the liquid exceeds about 35 percent, the solid beryllium particles are not capable of maintaining the structure intact and as a result thereof, sagging of the pressed compact may be observed. Hence, for a particular alloy, temperature ranges for sintering can be predicted from the phase diagram, and

Microstructure calculations are given for both quenched,

metastable and equilibrium structures 1n the following table.

PHASE IN BERYLLIUM-SILVER ALLOY Percent by Percent by Percent by Density of sintering weight of volume of volume of composite temp., C liquid liquid Be(partic1es) gms./cc.

60 percent by weight beryllium and 40 percent by weight silver 050 46. 5 20. 2 79. 8 2. 72 33. 3 66. 7 2. 72 1,150- 45. 2 54. 8 2. 72 1,200 70.0 30. 0 2. 72 1,225 2. 72 1,250 2. 72 Room temp. Equivalent 10.35 89. 35 2. 72

75 percent; by weight beryllium and 25 percent by weight silver 1,050 29. 1 l0. 5 89. 5 2. 29 33. 3 15.8 84. 2 2. 29 39. 6 23. 8 76. 2 2. 29 50.0 36. 8 63. 2 2. 29 1,225 63. 3 52. 7 47. 3 2. 29 Room temp. Equivalent. 5. 45 94. 5 2. 29 percent by weight beryllium and 15 percent by weight silver 1,05 17.7 5. 8 94.2 2.07 20. 3 8. 7 91. 3 2. 07 23. 5 12.6 87. 4 2. 07 30. 0 20.0 80.0 2. 07 37. 5 29.0 71.0 2. 07 ,250 75.0 68.0 32.0 2. 07 Room temp. Equivalent 2. 96.8 2. 07

It will be noted that the density values of the berylliumsilver composite are between the density of beryllium and the density of aluminum. Composites containing from about 60 to 75 percent, by Weight, of beryllium may be sintered from about 96 to about 99 percent of density by a single sinter. Composites containing about 85 percent, by weight, of beryllium require a double pressing and sintering operation to attain about 95 percent of theoretical density.

It was noted that upon cooling from the sintering temperature of the beryllium, the beryllium particles react with the silver rich liquid through a peritectic reaction whereby a new phase, delta, is formed below a temperature of about 1010 C. The delta phase which is in equilibrium with the solid beryllium between about 1010 C. and 850 C. contains about 18 percent, by weight, of beryllium. Additional cooling to a temperature between about 850 and about 760 C. results in reaction of the delta phase with solid beryllium particles to form a gamma phase in equilibrium with the beryllium particles. The gamma phase contains about 12 percent, by weight, of beryllium. At about 760 C., the gamma phase reacts with the beryllium particles so as to form substantially solid silver in equilibrium with substantially pure beryllium.

Since solid state reactions are generally slow, it is possible during normal cooling of beryllium-silver composite to retain either the gamma or the delta phase at room temperature due to sluggish diffusion. Since the presence of either the gamma phase or the delta phase in the micro structure of the composite would have a deleterious effect thereon from a ductility standpoint, either an isothermal hold of a predetermined time duration at 750 C. or a reheat to 750 C. is required to dissolve the gamma or the delta phase present in the microstructure. It has been found that the gamma or the delta phase may be dissolved by maintaining or reheating the alloy to 750 C. for about 24 hours. Also, it was found that it was possible to retain the elevated temperature structure and composition by quenching the alloy from a temperature above 1010 C. It is seen that quenching substantially eliminates the heat treatment step; however, quenching involves very rapid cooling rates.

Attention is directed to FIGURE 6, wherein a photomicrograph of 500 magnifications shows a composite of 25 percent, by weight, silver in beryllium after being etched by any suitable etching means such as dilute solution of ammonium hydroxide and hydrogen peroxide. The areas 60 are beryllium particles. The dark areas 61 are the intermediate delta or gamma phase surrounding the beryllium particles.

FIGURE 7 shows the appearance of the composite of 25 percent, by weight, silver in beryllium after heat treating at 750 C. in an argon atmosphere for about 24 hours. Note that the delta or the gamma phase has been removed. In the figure, the areas 70 are the sintered beryllium particles and the area 72 is the ductile silver-beryllium alloy matrix which surrounds the sintered beryllium particles.

Examples 1 and 7 show the expulsion of the liquid from a beryllium specimen and Examples 2-6 and 837 are illustrative of the preparation of beryllium composites by liquid phase Sintering.

EXAMPLE 1 Expulsion of the liquid aluminum-beryllium alloy from the solid beryllium specimen when the agent of lithium fluoride-lithium chloride or the agent of lithium fluoride is not used in the preparation of a beryllium-aluminum composite.

A mixture of about 70 percent, by weight, of beryllium having a particle size of 200 mesh or finer was ball mill mixed with about 30 percent, by weight, of aluminum powder of suitable particle size. The milled mixture was pressed by any siutable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It Was found that pressures of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density from about 50 to 60 percent of theoretical density and sufliciently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1000 C. for about 1 hour. This technique, due to the surface energies of the solid beryllium and the liquid formed, resulted in the expulsion of the liquid from the specimen 20 and its eventual freezing into rounded globs 21 on the surface of the specimen as shown in FIGURE 2.

EXAMPLE 2 (a) A composite of about 70 percent, by weight, beryllium and about 30 percent, by weight, of aluminum.

A mixture of about 70 percent, by Weight, of beryllium having a particle size of about 200 mesh or finer was ball mill mixed with about 30 percent, by weight, of aluminum powder of suitable particle size. Also ball mill mixed with the beryllium powder and the aluminum powder was about 1.0 percent, by weight, of the total metal additions of equal parts of a flux agent of lithium fluoride-lithium chloride. A mixture of beryllium powder and aluminum powder was also prepared, the lithium fluoride-lithium chloride agent constituting substantially 0.5 percent, by weight, of the total metal additions. The milled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressures of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density of from about 50 to 60 percent of theoretical density and sufiiciently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1000 centigrade for about 1 hour. The composition was then subjected to two represses followed by an intermediate sinter at 1000 for about one to two hours. An individual composite was prepared using the above mentioned procedure at each of the hereinafter enumerated temperatures of 800 and 1100 centigrade. Each of the composites was allowed to undergo equilibrium cooling to form a composite of beryllium particles dispersed in a matrix of pure aluminum. The overall composition was 70 parts, by weight, beryllium, and 30 parts, by weight, aluminum.

(b) The procedure of Example 2(a) was followed, using 70% by weight, of beryllium and 30%, by weight, of aluminum. Lithium fluoride alone was substituted for the lithium fluoride-lithium chloride fluxing agent, in about the same amount of 1.0%, by weight, of all of the metal additions to the amount of the beryllium.

EXAMPLE 3 A composite of about 50 percent, by weight, beryllium and about 50 percent, by weight, aluminum.

The procedures of Examples 2(a) and (b) were followed using 50 percent, by weight, of beryllium and 50 percent, by weight, of aluminum. An individual composite was prepared at each of the following temperatures of about 800, 1000 and 1100 C. using the aforementioned procedure.

EXAMPLE 4 A composite of about 60 percent, by weight, beryllium and about 40 percent, by weight, aluminum.

The procedures of Examples 2(a) and (b) were followed using about 60 percent, by weight, of beryllium and about 40 percent, by weight, of aluminum. An individual composite was prepared and :heated to one of the follow ing temperatures of about 800, 1000 and 1100 C.

EXAMPLE 5 A composite of about percent, by weight, beryllium and about 20 percent, by weight, aluminum.

The procedures of Examples 2(a) and (b) were followed using about 80 percent, by wcight, of beryllium and about 20 percent, by weight, of aluminum. An individual composite was prepared and heated to one of the following temperatures of about 800, 1000 and 1100 C.

EXAMPLE 6 A composite of about percent, by weight, beryllium and about 10 percent, by weight, aluminum.

The procedures of Examples 2(a) and (b) were followed using 90 percent, by weight, of beryllium and 10 percent, by weight, of aluminum. An individual composite was prepared at each of the following temperatures of about 800, 1000 and 1100 C. using the aforementioned procedure.

EXAMPLE 7 Expulsion of the liquid silver-beryllium alloy from the solid beryllium specimen when the agent of lithium fluoride-lithium chloride or the agent of lithium fluoride is not used in the preparation of a beryllium-silver com posite.

A mixture of about 75 percent, by weight, of beryllium having a particle size of 200 mesh or finer was ball mill mixed with about 25 percent, by weight, of silver powder of suitable particle size. The milled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressures of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density from about 50 to 60 percent of theoretical density and sufficiently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1150 C. for about 1 hour. This technique, due to the surface energies of the solid beryllium and the liquid formed, resulted in the expulsion of the liquid from the specimen and its eventual freezing into rounded globs on the surface of the specimen.

EXAMPLE 8 (a) A composite of about 60 percent, by weight, beryllium, and about 40 percent, by weight, of silver.

A mixture of about 60 percent, by weight, of beryllium having a particle size of 200 mesh or finer was ball mill mixed with about 40 percent, by weight, of silver powder of suitable particle size. Also ball mill mixed with the beryllium powder and the silver powder was about 1.0 percent, by weight, of the total metal additions equal parts of an agent of lithium fluoride-lithium chloride. Mixtures of beryllium and silver powders were also prepared, with the agent constituting substantially 0.5 and 2.0 percent, by weight of the total metal additions. The milled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressures of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density of from about 50 to 60 percent of theoretical density and sufficiently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1150 C. for about 1 hour. An individual composite was prepared using the abovementioned procedure at each of the here inafter enumerated temperatures of: 1050, 1100, 1200, 1225, and 1250 centigrade. Each of the composites was heat treated using the methods disclosed hereinafore.

(b) The procedure of Example 8(a) was followed, using 60%, by weight, of beryllium and 40%, by weight, of silver. Lithium fluoride alone was substituted for the lithium fluoride-lithium chloride fiuxing agent, in amounts of about 0.5% to 2.0%, by weight, of all of the metal additions to the amount of the beryllium.

EXAMPLE 9 A composite of about 75 percent, by weight, beryllium and about 25 percent, by weight, silver.

The procedures of Examples 8(a) and (b) were followed using about 75 percent, by weight, of beryllium and 25 percent, by weight, of silver. An individual composite was prepared at each of the following temperatures of about 1050, 1100", 1l50, 1200, l225 and 1250 C., using the aforementioned procedure.

EXAMPLE 10 A composite of about 85 percent, by weight, beryllium and about percent, by weight, silver.

The procedures of Examples 8(a) and (b) were followed using about 85 percent, by weight, of beryllium and about 15 percent, by weight, of silver. An individual composite was prepared and heated to one of the following temperatures of about 1050, 1100", 1150, 1200, 1225 and 1250 C.

The method of the present invention has been employed to advantage in producing by liquid phase sintering composites of particles of beryllium in a deformable metal matrix wherein the latter comprises alloys of aluminum, or of silver, or of both, with other deformable metal constituents, in addition to the presence therein of alloys of beryllium with matrix constituents. The following are examples of such additional composites.

EXAMPLE 11 A composite of about 70 percent, by weight, beryllium, 21 percent, by weight, aluminum, and the remainder silver. A mixture of about 70 percent, by weight, of beryllium powder having a particle size of 200 mesh or finer was ball mill mixed with about 30 percent, by weight, of an alloy of aluminum-silver powder of suitable particle size.

The alloy contains 70 percent, by weight, aluminum and 30 percent by weight, silver, Also ball mill mixed with the beryllium and alloy powders was about 1.0 percent, by weight, of the total metal additions equal parts of an agent of lithium fluoride-lithium chloride.Mixtures of the beryllium and alloy powders were also prepared with the agent constituting substantially 0.5 and 2.0 percent, by weight, of the total metal additions. The rnilled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressures of from 15,000 to 20,000 pounds per square inch resulted in a green compact having a density of from about 50 to 60 percent of theoretical density and sufficiently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1000 C. for about 1 hour. The composite is heat-treated at about 570 C. for about lhour so as to completely dissolve all the silver into the aluminum. The composite is then rapidly quenched so that the heat-treating temperature structure is preserved and the aluminum is supersaturated with silver. The solutionizing treatment contains all of the silver in solution. The silver can be precipitated from the supersaturated solid solution as a zeta phase.

EXAMPLE 12 the agent lithium fluoride-lithium chloride.

EXAMPLE 13 Acomposite of about 70 percent, by weight, beryllium, 21 percent, by weight, aluminum, and the remainder silver.

The procedure of Example 11 was followed using 70 percent, by weight, beryllium powder, mixed with about 30 percent, by weight, of an alloy powder of aluminumsilver. The alloy contains70 percent, by weight, aluminum and 30 percent, by weight, silver. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoridelithium chloride at a temperature of about 1100 C. using the aforementioned procedure- [EXAMPLE 14 A composite of about 50 percent, by weight, berryllium, 35 percent, by weight, aluminum, and the remainder silver.

The procedure of Example 11 was followed using 50 percent, by weight, beryllium powder, mixed with about 50 percent,by weight, of an alloy powder of aluminumsilver. The alloy contains 70 percent, by weight, aluminum and 30 percent, by weight, silver. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoridelithium chloride at temperatures of about 1000" and 1100 C. using the aforementionedprocedure.

EXAMPLE 15 A composite of about 60 percent, by weight, beryllium, 28 percent, by. weight, aluminum, and the remainder silver.

The procedure of Example 11- was followed using 60 percent, by weight, beryllium powder, mixed with about 40 percent, by weight, of an alloy powder of aluminumsilver. The alloy contains 70 percent, by weight, aluminum and 30 percent, by weight silver. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000 and 1100 C. using the aforementioned procedure.

13 EXAMPLE 16 A composite of about 75 percent, by weight, beryllium, 17.5 percent, by weight, aluminum, and the remainder silver.

The procedure of Example 11 was followed using 75 percent, by weight, beryllium powder mixed with about 25 percent, by weight, of an alloy powder of aluminumsilver. The alloy contains 70 percent, by weight, aluminum and 30 percent, by weight, silver. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000" and 1100" C. using the aforementioned procedure.

EXAMPLE 17 A composite of about 85 percent, by weight, beryllium, 15 percent, by weight, aluminum, and the remainder silver.

The procedure of Example 11 was followed using 85 percent, by weight, beryllium powder, mixed with about 15 percent by weight of an alloy powder of aluminumsilver. The alloy contains 70 percent, by weight, aluminum and 30 percent by weight, silver. Individual composites were prepared using 0.5, 1.0 and 2.0 percent, by weight, of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000 and 1100" C. using the aforementioned procedure.

EXAMPLE 18 A composite of about 75 percent, by weight, beryllium, 18 percent, by weight, silver, and the remainder copper.

A mixture of about 75 percent, by weight, of beryllium powder having a particle size of 200 mesh or finer was ball mill mixed with about 25 percent, by weight, of an alloy of silver-copper powder of suitable particle size. The alloy contains 72 percent, 'by weight, silver and 28 percent, by weight, copper. Also ball mill mixed with the beryllium and alloy powders was about 1.0 percent, by weight, of the total metal additions equal parts of an agent of lithium flouride-lithium chloride. Mixtures of the beryllium and alloy powders were also prepared with the agent constituting substantially 0.5, 1.0 and 2.0 percent, by weight, of the total metal additions. The milled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressures of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density of from about 50 to 60 percent of theoretical density and sufiiciently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1100" C. for about 1 hour. The composite is heat-treated at about 770" C. for about 1 hour so as to dissolve the copper into the silver. The composite is then rapidly quenched so that the heat-treating temperature structure is preserved and the silver is supersaturated with copper.

EXAMPLE 19 A composite of about 75 percent, by weight, beryllium, 18 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 75 percent, by weight, beryllium powder, 18 percent, by weight, silver powder, and the remainder copper powder. Individual composites were prepared using 0.5, 1.0 and 2.0 percent, by weight, of the total metal additions of the agent lithium fluoride-lithium chloride.

EXAMPLE 20 A composite of about 75 percent, by weight, beryllium, 18 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 75 percent, by weight, beryllium powder, mixed with about 25 percent by weight, of an alloy powder of silver-copper. The alloy contains 72 percent, by weight, silver and 28 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000" and 1150" C. using the aforementioned procedure.

EXAMPLE 21 A composite of about 75 percent, by weight, beryllium, 23 percent, by weight, silver and the remainder copper.

The procedure of Example 18 was followed using 75 percent, by weight, beryllium powder, mixed with about 25 percent, by weight, of an alloy powder of silver-copper. The alloy contains 92 percent, by weight, silver and 8 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent, by weight, of the total metal additions of the agent lithium fluoridelithium chloride at temperatures of about 1000", 1100" and 1150" C. using the aforementioned procedure.

EXAMPLE 22 A composite of about 5 0 percent, by weight, beryllium, 36 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 50 percent, by weight, beryllium powder, mixed with about 50 percent, by weight, of an alloy powder of silver-copper. The alloy contains 72 percent, by weight, silver and 28 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000", 1100'" and 1150 C. using the aforementioned procedure.

EXAMPLE 23 A composite of about 50 percent, by weight, beryllium, 46 percent, by weight, silver and the remainder copper.

The procedure of Example 18 was followed using 50 percent, by weight, beryllium powder, mixed with about 50 percent, by weight, of an alloy powder of silver-copper. The alloy contains 92 percent, by Weight, silver and 8 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000", 1100" and 1150" C. using the aforementioned procedure.

EXAMPLE 24 A composite of about 60 percent, by weight, beryllium, 28.8 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 60 percent, by weight, beryllium powder, mixed with about 40 percent, by Weight, of an alloy powder of silver-copper. The alloy contains 72 percent, by weight, silver and 28 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000", 1100" and 1150 C. using the aforementioned procedure.

EXAMPLE 25 A composite of about 60 percent, by weight, beryllium, 36.8 percent, by weight, silver and the remainder copper.

The procedure of Example 18 was followed using 60 percent, by weight, beryllium powder, mixed with about 40 percent, by weight, of an alloy powder of silver-copper. The alloy contains 92 percent, by weight, silver and 8 percent, by Weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000", 1100" and 1150" C. using the aforementioned procedure.

EXAMPLE 26 A composite of about 70 percent, by weight, beryllium, 21.60 percent, by Weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 70 percent, by weight, beryllium powder, mixed with about 30 percent, by weight, of an alloy powder of silver-copper. The alloy contains 72 percent, by weight, silver and 28 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000", 1100 and 1150 C. using the aforementioned procedure.

EXAMPLE 27 A composite of about 70 percent, by weight, beryllium, 27.6 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 70 percent, by weight, beryllium powder, mixed with about 30 percent, by weight, of an alloy powder of silver-copper. The alloy contains 92 percent, by weight, silver and 8 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000", 1100 and 1150 C. using the aforementioned procedure.

EXAMPLE 28 A composite of about 85 percent, by weight, beryllium, 10.8 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 85 percent, by weight, beryllium powder, mixed with about percent, by weight, of an alloy powder of silver. The alloy contains 72 percent, by weight, silver and 28 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about l000, 1100 and 1150 C. using the aforementioned procedure.

EXAMPLE 29 A composite of about 85 percent, by weight, beryllium, 13.8 percent, by weight, silver, and the remainder copper.

The procedure of Example 18 was followed using 85 percent, by weight, beryllium powder, mixed with about 15 percent, by weight, of an alloy powder of silver-copper. The allow contains 92 percent, by weight, silver and 8 percent, by weight, copper. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperature of about 1000, 1100 and 1150 C. using the aforementioned procedure.

EXAMPLE 30 A composite of about 75 percent, by weight, beryllium, 18 percent, by weilght, silver, and the remainder copper.

A mixture of beryllium powder having a particle size of 20 microns or finer was ball mill mixed with about 2.0 percent, by weight, of the total metal additions equal parts of an agent of lithium fluoride-lithium chloride. The milling was carried out with steel balls for about 1 hour. Thereafter, an alloy powder of 72 percent, by weight, silver and 28 percent, by weight, copper was ball mill mixed with the beryllium for about 1 hour. The beryllium constituted about 75 percent, by weight, of the blended powders and the alloy powder constituted about percent of the blended powders. Mixtures of the beryllium and alloy powder were also prepared with the agent having 0.5 and 1.0 percent, by weight, of the total metal additions. The milled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressures of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density of from about 50 to 60 percent of theoretical density and sufficiently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1150 C. for about 1 hour. The composite is heat-treated at about 770 C. for about 1 hour so as to dissolve the copper into the silver. The

composite is then rapidly quenched so that the heattreating temperature structure is preserved and the silver is supersaturated with copper. It was found that the composite had a density of about 99.92 percent of theoretical density.

EXAMPLE 31 A composite of about 70 percent, by weight, beryllium, 27 percent, by weight, aluminum, and the remainder magnesium.

A mixture of about 70 percent, by weight, beryllium powder having a particle size of 200 mesh or finer was ball mill mixed with about 30 percent, by weight, of an alloy of aluminum-magnesium powder of suitable particle size. The alloy contains percent, by weight, aluminum and 10 percent, by weight, magnesium. Also ball mill mixed with the beryllium and alloy powders was about 1.0 percent, by weight, of the total metal additions equal parts of an agent of lithium fluoride-lithium chloride. Mixtures of the beryllium and alloy powders were also prepared with the agent constituting substantially 0.5 percent, by weight, of the total metal additions. The milled mixture was pressed by any suitable means such as by an automatic press at a suitable pressure to provide a green compact sturdy enough to be handled. It was found that pressure of from about 15,000 to 20,000 pounds per square inch resulted in a green compact having a density of from about 50 to 60 percent of theoretical density and sufficiently strong to be handled. Sintering of the compact was carried out in an argon atmosphere at about 1000 C. for about 1 hour. The composite is heat-treated at about 450 C. for about 1 hour so as to completely dissolve all the magnesium into the aluminum. The composite is then rapidly quenched so that the heat-treating temperature structure is preserved and the aluminum is supersaturated with magnesium. The solutionizing treat- \ment contains all of the magnesium in solution. The magnesium can be precipitated from the supersaturated solid solution as a zeta phase.

EXAMPLE 32 A composite of about 70 percent, by weight, beryllium, 27 percent, by weight, aluminum, and the remainder magnesium.

The procedure of Example 31 was followed using 70 percent, by weight, beryllium powder, 27 percent, by weight, aluminum powder, and the remainder magnesium powder. Individual composites were prepared using 0.5 and 2.0 percent, by weight, of the total metal additions of the agent lithium fluoride-lithium chloride.

EXAMPLE 33 EXAMPLE 34 A composite of about 50 percent, by weight, beryllium, 45 percent, by weight, aluminum, and the remainder magnesium.

The procedure of Example 31 was followed using 50 percent, by weight, beryllium powder, mixed with about 50 percent, by weight, of an alloy powder of aluminummagnesium. The alloy contains 90 percent, by weight, aluminum and 10 percent, by weight, magnesium. Individual composites were prepared using 0.5, 1.0 and 2.0 percent, by weight, of the total metal additions of the agent lithium 1 7 fluoride-lithium chloride at temperatures of about 1000 and 1100f C. using the aforementioned procedure.

EXAMPLE 35 A composite of about 60 percent, by weight, beryllium, 36 percent, by weight, aluminum, and the remainder magnesium.

The procedure of Example 31 was followed using 60 percent, by weight, beryllium powder, .mixed with about 40 percent, by weight, of an alloy powder of aluminummagnesium. The alloy contains 90 percent, by weight, aluminum and percent, by weight, magnesium. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000 and 1100 C. using the aforementioned procedure.

EXAMPLE 36 A composite of about 75 percent, by weight, beryllium, 22.5 percent, by weight, aluminum, and the remainder magnesium.

The procedure of Example 31 was followed using 75 percent, by weight, beryllium powder, mixed with about 25 percent, by weight, of an alloy powder of aluminummagnesium. The alloy contains 90 percent, by weight, aluminum and 10 percent, by weight, magnesium. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about l000 and 1100 C. using the aforementioned procedure.

EXAMPLE 3 7 A composite of about 85 percent, by weight, beryllium, 13.5 percent, by weight, aluminum, and the remainder magnesium.

The procedure of Example 31 was followed using 85 percent, by weight, beryllium powder, mixed with about percent, by weight, of an alloy powder of aluminummagnesium. The alloy contains 90 percent, by weight, aluminum and 10 percent, by weight, magnesium. Individual composites were prepared using 0.5, 1.0 and 2.0 percent by weight of the total metal additions of the agent lithium fluoride-lithium chloride at temperatures of about 1000 and 1100 C. using the aforementioned procedure.

It has been indicated herein that while the sintering temperature at which the pressed green compact is heated is to be below the melting point of beryllium it must also be above the melting point of the eutectic of the beryllium and the deformable metal constituent. This eutectic melting point lower limit is used in the sense that it identifies the lowest melting point of the deformable metal matrix of the composite in which beryllium particles are ultimately encased regardless of the constitution of this matrix developed during the sintering; i.e., whether such matrix may be wholly such an eutectic, or a mixture of such eutectic and the deformable metal constituent, or essentially the latter.

The present invention is not intended to be limited to the disclosure herein, and the changes and modifications may be made in the disclosure by those skilled in the art without departing from the spirit and scope of the novel concepts of this invention. Such modifications and variations are considered to be within the purview and scope of this invention and the appended claims.

Having thus described our invention, we claim:

1. A method of producing by liquid phase sintering composites of particles of beryllium in a deformable metal matrix, said method comprising the steps of: mixing an amount of beryllium powder, an amount of powder of a deformable metal constituent and a minor quantity of powdered fiuxing agent selected from the group consisting of alkali and alkaline earth metal halogenides to form a powdered mixture; the amount of beryllium powder being in the range of about 50% to 90%, by weight, of the mixture, the amount of powdered agent constituting no greater than about a few percent, by weight, of the mixture and the amount of powder of the deformable metal constituent constituting essentially the remainder, by weight, of the mixture; confining and pressing the resulting powdered mixture to form a green compact; and heating said green compact in a substantially non-oxidizing environment to a sintering temperature below the melting point of beryllium and above the beryllium and deformable metal constituent eutectic melting point to produce a composite of beryllium particles surrounded by a deformable envelope of matrix metal, said agent providing, during the sintering of the compact, a favorable surface energy equilibrium between the particles of beryllium and the melted deformable metal constituent whereby expulsion of said deformable metal constituent from the composite is prevented and substantially all of the agent is eventually eliminated by vaporization during the sintering.

2. The method as claimed in claim 1, in which said agent comprises lithium fluoride.

3. The method as claimed in claim 2, in which said agent is a mixture of lithium fluoride and lithium chloride.

4. The method as claimed in claim 3, in which the components of said lithium fluoride-lithium chloride agent are in a weight ratio of about one to one.

5. The method as claimed in claim 1, in which the deformable metal constituent comprises powder aluminum as its major component, and in which said agent is in an amount about 0.5 to 1.0 percent, by weight, of the powdered mixture.

6. The method as claimed in claim 5, in which said agent comprises lithium fluoride.

7. The method as claimed in claim 6, in which said agent is a mixture of lithium fluoride and lithium chloride.

8. The method as claimed in claim 5, in which said agent is composed of about equal parts by weight of lithium fluoride and lithium chloride and said heating of the compact is performed in a non-oxidizing environment at a temperature of about 800 C. to 1100 C. for about one hour.

9. The method as claimed in claim 8, in which said powder beryllium constitutes about 70%, by weight, and said agent constitutes about 1%, by weight, of the powdered mixture.

10. The method of producing a beryllium-aluminum composite by liquid phase sintering, said method comprises the steps of: mixing predetermined portions of powder beryllium and powder aluminum together with a predetermined portion of an agent selected from the group consisting of alkali and alkaline earth halogenides; pressing said portions within the confines of a die means so as to form a green compact; heating said green compact to the sintering temperature of said beryllium, said agent providing a favorable surface energy equilibrium between said beryllium and said aluminum so that said aluminum progressively dissolves said beryllium at the beryllium sintering temperature thereby forming a beryllium composite of beryllium particles surrounded by an alloy of aluminum-beryllium; and quenching said composite to preserve the phase relations existing at said sintering temperature.

11. The method as claimed in claim 10, in which said predetermined portion of beryllium is about 50 to percent, by weight, and the remainder aluminum, and said agent about 0.5 to 1.0 percent, by weight, of the total metal additions.

12. The method as claimed in claim 10, in which said agent is lithium fluoride-lithium chloride.

13. The method as claimed in claim 12, in which said lithium fluoride-lithium chloride agent is in about a one to one ratio.

14. The method as claimed in claim 10, in which said heating of said beryllium, said aluminum, and said agent is in an argon atmosphere at a temperature of about 800 C. to 1100 C. for about 1 hour.

15'. The method as claimed in claim 10, in which said predetermined portion of beryllium is 70 percent, by

19 weight, and the remainder aluminum, and said agent 1 percent, by weight, of the total metal additions.

16. The method as claimed in claim 15, in which said agent is composed of equal parts of said lithium fluoride and said lithium chloride.

17. A method for producing composites of beryllium in an amount of about 50 to about 90 weight percent in a deformable metal matrix comprising heating a powdery admixture of beryllium and the deformable metal at a temperature below the melting point temperature of beryllium and above the eutectic melting point temperature of said admixture in the presence of a vaporizable flux selected from the group consisting of alkali and alkaline earth halogenides in an amount of from about a trace to a few weight percent.

18. The method of claim 17, wherein said heating of said admixture is performed in a non-oxidizing atmosphere at a temperature of about 800 C. to about 1250 C.

19. The method of claim 18, further including the step of compacting said admixture, prior to heating, whereby a green compact is provided.

20. The method of claim 18, wherein said agent is selected from the group consisting of lithium fluoride or a mixture of lithium fluoride and lithium chloride.

21. The method of claim 20, wherein said deformable metal constituent is selected from the group consisting of 20 aluminum, silver, alloys of aluminum, alloys of silver and alloys of aluminum-silver.

22. The method of claim 20, wherein said agent is about 0.5 to about 2.0, by weight, of the admixture.

23. The method of claim 22, wherein said beryllium is about 70%, by weight, said agent about 1%, by weight, remainder essentially the deformable metal constituent of the admixture.

References Cited UNITED STATES PATENTS 1,988,861 l/l935 Cherausch 752-00 X 2,167,240 7/ 1939 Hensel 75200 X 3,232,754 2/1966 Storchhein 75214 3,264,147 8/ 1966 Bonfield 75150 X 3,303,559 3/1967 Holtsclaw 75-200 X 3,337,334 8/1967 Fenn 7515O 3,337,336 8/1967 Rao 75-222 X 3,350,201 10/1967 Ang 75-226 X FOREIGN PATENTS 707,156 4/1954 Great Britain.

CARL D. QUARFORTH, Primary Examiner A. J. STEINER, Assistant Examiner US. Cl. X.R. 75-214

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