真空压铸Mg-6Gd-3Y-0.5Zr镁合金的组织与性能(英文)

Microstructure and mechanical properties of Mg-6Gd-3Y-0.5Zr alloy processed by high-vacuum die-casting

采用真空压铸工艺制备GW63K合金,研究压射速度和真空度对组织及性能的影响。采用光学显微镜、SEM及EDX对组织进行观察。研究GW63K的热处理工艺。结果表明:铸态GW63K合金由α-Mg基体和Mg24(Gd,Y)5第二相组成,且随着压射速度的增加,合金的屈服强度没有大的变化,但是伸长率先增加后减小;真空辅助能够减少气孔的大小及含量。在475°C固溶2 h,然后在200°C下时效80 h,GW63K合金的抗拉强度和伸长率分别达到308 MPa和9.45%。首次发现预初晶(ESCs)的存在对压铸GW63K合金热处理性能有巨大影响,预初晶(ESCs)的存在严重降低热处理后合金的性能。

GW63K （Mg-6Gd-3Y-0.5Zr） magnesium alloys were prepared successfully by high-vacuum die-casting. Effects of fast shot speed and vacuum level on the grain size and mechanical properties of this alloy were studied. Microstructure of the alloys was analyzed by SEM, EDX and optical microscope （OM）. The effect of heat treatment on high vacuum die-casting （HVDC） GW63K alloy was also studied. The results indicate that with the increase of fast velocity, the tensile yield strength hardly changes, but the elongation first increases, then decreases. The optimum heat treatment process is solution treatment at 748 K for 2 h and aging at 473 K for 80 h. Under this condition, GW63K magnesium alloy exhibits a maximum tensile strength and elongation of 308 MPa and 9.45%. There is significant correlation between ductility and the presence of external solidified cells （ESCs）. The as-cast GW63K alloy consists ofα-Mg and Mg24（Gd,Y）5 particles. After heat treatment, Gd and Y atoms dissolve intoα-Mg matrix.