砂型铸造ZL205A合金组织与力学性能的研究

Microstructure and Mechanical Properties of ZL205A Alloy in Sand Casting

研究了砂型铸造ZL2 0 5A合金在铸态和热处理 (T6)态下合金的显微组织和力学性能。结果表明 :铸态ZL2 0 5A合金基体相为α(Al)固溶体 ,枝晶间和晶界上有α(Al)、θ(Al2 Cu)相和Cd相的共晶组织。晶界处存在θ和T(Al12 CuMn2 )相的混合组织。另外 ,还有少量的灰色块状ZrAl3 相、条状Al3 Ti相分布在α固溶体上。合金中添加的少量Ti、V、Zr和B等元素 ,可有效地细化晶粒。T6固溶处理时 ,θ相和Cd相溶入α固溶体中 ,二次T相呈弥散小质点析出 ,组织中还存在片状Al3 Ti的偏析物和未完全溶解残留在晶界上的Al2 Cu相。合金 (T6)抗拉强度随温度的升高呈下降的趋势 ,合金在不同温度下均为延展性断裂 。

Microstructure and mechanical properties of as-cast and heat treated (T6) ZL205A alloy in sand casting were studied.Phase constituents of as-cast ZL205A alloy were composed of matrix phase of α(Al) solid-solution,of eutectic structure of α(Al),θ(Al_2Cu),Cr phase in dendrite and grain boundary,and of mixture structure of θ and T(Al_(12)CuMn_2) phase on grain boundary as well as a little grey bulk ZrAl_3 and strip Al_3Ti phase in α(Al) solid-solution.Minor addition of Ti,V,Zr and B into the alloy can significantly refine the grain size.θ phase and Cr phase were dissolved into α(Al) solid-solution and secondary dispersed T phase can be precipitated from the T6 treated alloy.Meanwhile,there exist laminar Al_3Ti segregation and retained Al_2Cu phase in crystal boundary.The tensile strength of T6 treated alloy with good toughness which is ductile fracture at different temperatures decreases with temperature increase.