Aging process of TiC_p/Al-Mg-Si composites

Aging processes of TiC particle dispersed Al-1%Mg₂Si composite materials were investigated by Vickers micro-hardness measurement, and transmission electron microscope (TEM) observation. At relatively lower aging temperature, the Vickers micro-hardness curves of each composite materials had a similar tendency with that of the matrix alloy. The size and distributions of the precipitates in the composite material were almost same to those of the matrix alloy. At higher aging temperature, aging time to reach a maximum hardness in the 4 vol%TiC composite materials was shortened as compared with those of the matrix alloy. At the aging temperature, age hardening was scarcely observed in 8%TiC composite materials. By the TEM observation, relatively large size of needle- or rod-like precipitates were observed in 4 vol%TiC composite material, while very coarse rod-like precipitates were sparsely distributed in 8 vol%TiC composite material. At more elevated temperature, the very coarse rod-like precipitates were observed in both the composite materials, consequently, the age hardening could not be detected on the hardness curves of the materials. The small amount of dislocations which were probably introduced by quenching after solid solution treatment were observed near the TiC particles. The precipitates near the particles were especially coarsened.