Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报

ZHONGGUO YOUSEJINSHU XUEBAO

第28卷    第7期    总第232期    2018年7月

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文章编号:1004-0609(2018)-07-1309-11
Mg-6Zn-xCu-0.6Zr合金凝固路径及热裂倾向性
王 志,李一洲,刘 正,周 野,王 峰,毛萍莉

(沈阳工业大学 材料科学与工程学院,沈阳 110870)

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、MgZn2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。

 

关键字: 镁合金;热裂倾向性;合金凝固路径;凝固温度区间

Solidification path and hot tearing tendency of Mg-6Zn-xCu-0.6Zr alloys
WANG Zhi, LI Yi-zhou, LIU Zheng, ZHOU Ye, WANG Feng, MAO Ping-li

School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870, China

Abstract: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 thermocouples thermal analysis. 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 α-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.

 

Key words: Mg alloy; hot tearing tendency; solidification path; solidification temperature range

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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