Hf. Lee et al., HIGH DEFORMATION CONSOLIDATION POWDER-METALLURGY PROCESSES FOR AN AL-LI ALLOY COMPOSITE, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 189(1-2), 1994, pp. 173-180
High deformation consolidation powder metallurgy (PM) processes for AI
-Li alloy composites use a high degree of deformation and relatively h
igh strain rates for consolidation, thus eliminating the problem of Li
depletion. In this work, a PM process involving cold isostatic pressi
ng at 350 MPa followed by hot extrusion at about 500 degrees C was use
d to produce 8091 Al-Li composites reinforced with particulate SiC. Di
fferent particle sizes of SiC were used. The composite materials posse
ss increased modulus and hardness with increasing SiC content. Smaller
reinforcement particles gave higher increases. However, the smallest
particles used, 2.5 mu m, introduced agglomeration problems. Increasin
g the SiC reinforcement content did not increase the yield stress and
strain, but decreased the ultimate stress and fracture strain. This wa
s attributed to the possibility that the SiC particles, by being fract
ured in the consolidation process, acted as crack initiation points as
well as stress concentration points. The results also indicate the li
mitations of using such a particle reinforcement system.