Aluminum-lithium-beryllium alloys have been prepared by melt spinning, using prealloyed arc-melted buttons. The alloy ribbon was comminuted and cold compacted to 30 to 50% density, vacuum hot pressed to 100% density, and extruded. The bar product was subsequently solution heat treated, quenched, and aged. The microstructure of the alloys consists of a relatively featureless matrix containing a homogeneous dispersion of fine beryllium particles, mostly 50 to 500 nm in size. The results of heat treatment show that the alloys respond to age hardening in a manner similar to that of binary Al-Li alloys. Preliminary results on the mechanical properties and their relationships with microstructural features are presented for the Al-Li-Be alloys, as well as their potential for weight savings. The authors estimate that these monolithic aluminum alloys may exhibit specific strength and elastic modulus values comparable to those of the best whisker or particulate metal-matrix composites, while showing concomitant high weight savings.

The development of a submicron boron nitride coating has substantially improved the stability of boron filaments in metallic matrices. It is now possible to think in terms of continuous casting techniques for the fabrication of low melting metal matrix composites like aluminum/ boron. The boron nitride coating also contributes to the formation of void-free nickel/boron composites by electroforming processes, and reaction-free nickel/boron and titanium/boron composites by diffusion bonding methods. Mechanical properties of 60-70 vol. % nitrided boron/6061 aluminum composites prepared by continuous liquid infiltration are discussed. The effects of heat treatment on these composite strengths are also considered.

The development of a submicron boron nitride coating for boron filaments has made possible the production of boron-aluminum com posites by a continuous casting technique. The tensile properties of aluminized boron filaments, as well as composite modules and tapes, fabricated by this liquid infiltration process are evaluated in this investigation. Tensile strengths up to 297 ksi were obtained for 65 volume percent nitrided boron-6061 aluminum alloy composite modules. Thermomechanical treatment in air of early 16-filament modules showed no degradation in strength after one hour at 1050°F, or 1000 hours at 570°F. Seven inches square panels, fabricated by diffusion bonding 20 mil diameter modules, exhibited longitudinal tensile strengths as high as 187 ksi and transverse strengths up to 15 ksi for fiber volume fractions of approximately 50 percent. The use of Ti cladding on aluminum-boron panel surfaces increased the trans verse strength to 33 ksi.

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