High deformation consolidation powder metallurgy processes for an AlLi alloy composite

High deformation consolidation powder metallurgy (PM) processes for AlLi alloy composites use a high degree of deformation and relatively high strain rates for consolidation, thus eliminating the problem of Li depletion. In this work, a PM process involving cold isostatic pressing at 350 MPa followed by hot extrusion at about 500°C was used to produce 8091 AlLi composites reinforced with particulate SiC. Different particle sizes of SiC were used. The composite materials possess increased modulus and hardness with increasing SiC content. Smaller reinforcement particles gave higher increases. However, the smallest particles used, 2.5 μm, introduced agglomeration problems. Increasing the SiC reinforcement content did not increase the yield stress and strain, but decreased the ultimate stress and fracture strain. This was attributed to the possibility that the SiC particles, by being fractured in the consolidation process, acted as crack initiation points as well as stress concentration points. The results also indicate the limitations of using such a particle reinforcement system.