Fabrication of metal-matrix composites by hot-triaxial-compaction of foil/fiber/foil lay-ups

Hot triaxial compaction was used to consolidate Ti-6Al-4V matrix, SCS-6 silicon carbide fiber composites in order to examine the effect of stress state on the densification process. In order to compensate for local density variations, the residual porosity was expressed as the total pore area normalized by the total number of fibers. It was found that the applied stress state influences the consolidation behavior. Specifically, for fixed temperature, time, fiber spacing, and vertical principal stress the densification rate increases as the added axial stress is increased in comparison to the hydrostatic pressure. This observation was attributed to the increase of the effective stress over the mean stress, and the decreased transverse constraint on the composite which allows easier lateral fiber movement and small increases of the fiber spacing.