摘要
基于修正的Clyne-Davies热裂模型(CSC~*),对Mg-6Zn-xCu-0.6Zr(x%=0,1%,2%,3%,质量分数)合金热裂倾向性进行预测;采用双电偶热分析法研究Mg-6Zn-xCu-0.6Zr合金凝固路径、凝固过程中的特征温度、枝晶干涉固相分数等。利用"T"型热裂模具测试系统采集Mg-6Zn-xCu-0.6Zr合金凝固收缩力随温度(或时间)的变化曲线。实验结果与CSC~*预测值均表明合金的热裂倾向性随着Cu含量的增加而减小。Cu元素的加入使初生α-Mg相的析出温度降低、MgZn_2相的析出温度升高,从而使合金的凝固温度区间变窄,降低合金的热裂倾向性。Mg-6Zn-(0,1)Cu-0.6Zr合金热裂纹断口主要为液膜和分离的自由枝晶臂。Mg-6Zn-(2,3)Cu-0.6Zr合金断口表面生成大量的低熔点共晶相,液膜较厚,增强残余液相对分离的枝晶补缩能力,降低合金的热裂倾向性。
Hot tearing tendency of Mg-6Zn-xCu-0.6Zr (x%=0, 1%, 2%, 3%, mass fraction) alloys were predicted based on modified Clyne-Davies model (CSC*). The solidification path, characteristic temperature during solidification, the solid fraction in coherent dendrite point of Mg-6Zn-xCu-0.6Zr alloys were studied by the double tkermocouples thermal mmlysis. The curve of solidification contraction stress with temperature (or time) of Mg-6Zn-xCu-0.6Zr alloys were measured using the "T" type hot tearing permanent-mold. The results show that the CSC* prediction values are in good agreement with the experimental results. The hot tearing tendency decreases with increasing Cu content. The precipitation temperature of primary a-Mg phase decreases and the precipitation temperature of MgZn2 phase increases by addition of Cu element, thus shortening the solidification temperature range of alloys and decreasing the hot tearing tendency. The hot cracking fractures of Mg-6Zn- (0,1) Cu-0.6Zr alloys are mainly occupied by the liquid film and separated free dendrite arm. A large number of eutectic phase with low melting point and the thicker liquid film were observed on the fracture surfaces of Mg-6Zn- (2,3) Cu-0.6Zr alloys which enhances the feeding ability and reduces the hot tearing tendency.
作者
王志
李一洲
刘正
周野
王峰
毛萍莉
WANG Zhi;LI Yi-zhou;LIU Zheng;ZHOU Ye;WANG Feng;MAO Ping-li(School of Materials Science and Engineering,Shenyang University of Technology,Shenya~g 110870,China)
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2018年第7期1309-1319,共11页
The Chinese Journal of Nonferrous Metals
基金
国家自然科学基金资助项目(51504153
51571145)
辽宁省教育厅科学技术研究一般项目(L2015397)~~
关键词
镁合金
热裂倾向性
合金凝固路径
凝固温度区间
Mg alloy
hot tearing tendency
solidification path
solidification temperature range