Aging microstructural characteristics of ZA-27 alloy and SiC p/ZA-27 composite

Abstract

Abstract The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiC p/ZA-27 composite(ZMC p) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ZMC p continuously change during aging process. Little tiny spherical Zn-rich η phase distributes in the dendrite. Amount of transitional α′ phase, well coherent with equilibrium α f phase, in SiC p-neighboring dendrite edge zone is less than that in dendrite center zone. Both eutectic and peritectic β phase transform into lamellar α and η phases, obeying [ 2 ¯ 113 ] η / / [ 110 ] α , and ( 002 ) α / / ( 1 1 ¯ 01 ) η . In the like-eutecticum of ZMC p, less amount of β phase and decomposition products are found. The size of α phase decomposed from peritectic β phase in ZMC p is obviously larger than that in the monolithic alloy. The lamella decomposition of β phase beside SiC p is evidently more rapid than that in the alloy. SiC particulates strongly accelerate neighboring β phase decomposition in aging process.