Ca对Mg-Zn合金热裂敏感性的影响

为了研究Ca元素对Mg-Zn二元合金热裂敏感性的影响,采用自制的“T”字形热裂仪器,以Mg-1.5Zn合金为基础合金,通过添加1%~4%的Ca元素来研究Mg-Zn-Ca系合金的热裂行为.采用金相显微镜及扫描电镜观察热裂区域的显微组织,分析Mg-Zn-Ca三元合金的热裂形成机理.结果表明,对于Mg-1.5Zn-xCa合金而言,随着Ca添加量的增加,热裂纹体积不断减小,合金的热裂敏感性降低; 热裂发生时,Mg-1.5Zn-xCa合金中剩余液相体积分数逐渐增加,补缩效果不断提高,热裂敏感性随着Ca添加量的增加而逐渐降低; 对于Mg-Zn-Ca合金而言,裂纹处的补缩物质为α-Mg和Ca₂Mg₆Zn₃、Mg₂Ca相的混合物.

Effect of Ca on hot tearing susceptibility of Mg-Zn alloy

In order to clarify the effect of Ca element on the hot tearing susceptibility of Mg-Zn binary alloy, the hot tearing behaviour of Mg-Zn-Ca series alloys was investigated with the self-made “T” type hot tearing testing device through taking Mg-1.5Zn magnesium alloy as a base alloy and adding 1% to 4% Ca element. The microstructures in the hot tearing regions were observed with optical microscope and scanning electron microscope(SEM). In addition, the hot tearing mechanism of Mg-Zn-Ca ternary alloys was analyzed. The results indicate that for the Mg-1.5Zn-xCa alloys, the volume of hot cracks gradually decreases and the hot tearing susceptibility of the alloys reduces with increasing the content of Ca element. When the hot tearing occurs, the volume fraction of residual liquid phase in the Mg-1.5Zn-xCa alloys gradually increases, and thus, the feeding effect continuously increases. Moreover, the hot tearing susceptibility gradually decreases with increasing the content of Ca element. For the Mg-Zn-Ca alloys, the feeding materials in the crack regions are the mixture of α-Mg, Ca₂Mg₆Zn₃ and Mg₂Ca phases.