Ca含量对Mg-5Al-10Zn-xCa镁合金组织与力学性能的影响

Effects of Ca Content on Microstructure and Mechanical Properties of Mg-5Al-10Zn-xCa Magnesium Alloys

采用重力铸造法制备了Mg-5Al-10Zn-xCa(x=0,0.25,0.5,0.75,1.0,1.25,1.5,质量分数,%)镁合金。通过X射线衍射仪、光学显微镜和扫描电镜等研究了Ca含量对合金组织与力学性能的影响。结果表明:铸态Mg-5Al-10Zn-xCa合金主要由α-Mg基体、β-Mg17Al12、Mg32(Al,Zn)49、MgZn2和Al2Ca相组成。当Ca含量从0.25%增加到1.25%时,β-Mg17Al12相由粗大的网状转变为细小的网状分布于晶界上,基体晶粒显著细化,此时合金的室温抗拉强度达到最大值157 MPa,较未加Ca时提高了49.5%;Ca含量继续增加至1.5%,晶粒及β-Mg17Al12相又发生粗化,抗拉强度发生下降;拉伸断裂形式均为准解理脆性断裂。

Mg-5Al-10Zn-xCa(x=0,0.25,0.5,0.75,1.0,1.25,1.5wt%)magnesium alloys were prepared by gravity casting method.The effects of Ca content on the microstructure and mechanical properties of the alloy were investigated by XRD,OM and SEM.The results show that the as-cast Mg-5Al-10Zn-xCa alloy is mainly composed ofα-Mg matrix,β-Mg17Al12,Mg32(Al,Zn)49,MgZn2 and Al2Ca phases.With the increase of Ca content from 0.25%to 1.25%,theβ-Mg17Al12 phase changes from coarse network to fine network,which distributed at the grain boundaries,the grain is obviously refined,meanwhile,the tensile strength of the alloy at room temprature reaches the maximum,that is 157 MPa,increased by 49.5%,respectively,compared with that of the alloy without Ca addition.When the Ca content reaches 1.5%,the grain andβ-Mg17Al12 phase are coarsened once more,meanwhile,the tensile strength decreases.The tensile fracture mode of the alloys are characterized by quasi-cleavage brittle fracture.