Aging microstructural characteristics of ZA-27 alloy and SiCp/ZA-27 composite

The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiCp/ZA-27 composite(ZMCp) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ZMCP continuously change during aging process. Little tiny spherical Zn-rich eta phase distributes in the dendrite. Amount of transitional a' phase, well coherent with equilibrium a(f) phase, in SiCp-neighboring dendrite edge zone is less than that in dendrite center zone. Both eutectic and peritectic beta phase transform into lamellar a and eta phases, obeying [2113](eta)//[110](a), and (002)(a)// (1 (1) over bar 01), In the like-eutecticum of ZMC(p) less amount of beta phase and decomposition products are found. The size of a phase decomposed from peritectic, beta phase in ZMCp is obviously larger than that in the monolithic alloy. The lamella decomposition of, beta phase beside SiCP is evidently more rapid than that in the alloy. SiC particulates strongly accelerate neighboring beta phase decomposition in aging process.