Mg-xGd-1Er-0.5Zr合金热裂敏感性研究  

Investigations on hot cracking susceptibility of Mg-xGd-1Er-0.5Zr alloys

作　　者：伍迪灿 王云峰 杜文博[1] 丁宁[1] 李淑波[1] 朱训明 王朝辉[1] WU Di-can;WANG Yun-feng;DU Wen-bo;DING Ning;LI Shu-bo;ZHU Xun-ming;WANG Zhao-hui(Faculty of Materials and Manufacturing,Beijing University of Technology,Beijing 100124,China;Weihai Wanfeng Auto Holding Group Co.,Ltd.,Weihai 264209,China)

机构地区：[1]北京工业大学材料与制造学部,北京100124 [2]威海万丰镁业科技发展有限公司,威海264209

出　　处：《中国有色金属学报》2022年第2期375-385,共11页The Chinese Journal of Nonferrous Metals

基　　金：国家重点研发计划资助项目(2016YFB0301001);国家重点研发计划资助项目(2016YFB0301101);北京市教委科技发展基金资助项目(KZ201810005005)。

摘　　要：本文基于Clyne-Davies模型评价了Mg-xGd-1Er-0.5Zr(x=8.0、10.0、12.0,质量分数,%)合金的热裂敏感性,并利用“约束杆”铸造钢模实验方法验证了该合金的热裂倾向。结果表明基于Clyne-Davies模型得到的计算结果能有效预测Mg-xGd-1Er-0.5Zr合金热裂敏感性,且随着Gd含量的增加,合金的热裂敏感性下降。采用数据采集系统、电子显微镜及X射线衍射仪等手段,对铸件凝固曲线、微观组织和析出相进行了分析,发现随着Gd含量的增加,合金的热裂敏感性降低,其原因是凝固后期Mg_(5)(Gd,Er)共晶液相的增多有利于枝晶间裂纹的补缩。此外,共晶液相也会抑制α-Mg枝晶的形核长大,使合金的凝固温度区间减小,从而降低合金的热裂敏感性。对热裂断口进行分析后认为,断口出现的液膜以及晶间搭桥提高了晶间结合力,这是热裂敏感性降低的另一个重要原因。Hot tearing is a potential problem that deteriorates the ductility of Mg castings.The effects of Gd content on the hot cracking susceptibility(H)of Mg-xGd-1Er-0.5Zr(x=8.0,10.0,12.0,mass fraction,%)were predicted based on the Clyne-Davies model,and verified by using the“constraint rod”permanent mold test.The results show that the variation of H value of the Mg-xGd-1Er-0.5Zr alloys can be effectively predicted by the Clyne-Davies model and the theory values are in consistent with the experimental ones.The microstructure and the precipitates in the as-cast Mg alloys were analyzed by scanning electron microscopy(SEM)and X-ray diffractometery(XRD).It is demonstrated that the H value decreases with the increase of Gd content.The higher Gd contents lead to the increase of the volume fraction of Mg_(5)(Gd,Er)eutectic phase,which is facilitated to feed the micro-cracks between the dendrite arms during the terminal solidification stage,so as to decrease the H value.In addition,the eutectic phase also inhibits the nucleation and growth ofα-Mg dendrites and thus reduces the solidification temperature range of the alloy.Combined with the fracture surface observation,it is suggested that the liquid film and bridge between the grains during solidification improve the grain-binding force,which is also considered as another important reason responsible for reducing the H value.

关 键 词：Mg-Gd-Er-Zr合金 凝固 微观组织 热裂模型 热裂敏感性 

分 类 号：TG146.22[一般工业技术—材料科学与工程]