Mg-7Zn-xCu-0.6Zr合金熱裂行為的研究

Mg-7Zn-xCu-0.6Zr合金熱裂行為的研究INVESTIGATIONS ON HOT TEARING OF Mg-7Zn-xCu-0.6Zr ALLOYS

采用“T”型熱裂模具研究了不同含量Cu元素對Mg-7Zn-0.6Zr合金熱裂行為的影響。利用X射線衍射和掃描電子顯微鏡對Mg-7Zn-xCu-0.6Zr（x=0，1，2，3）合金進(jìn)行了顯微組織和熱裂區(qū)域組織形貌觀察。通過測量熱裂紋體積表征了Mg-7Zn-xCu-0.6Zr（x=0，1，2，3）合金的熱裂傾向性。實(shí)驗(yàn)結(jié)果表明，Mg-7Zn-0.6Zr系合金中隨著Cu含量的增加，晶粒得到細(xì)化，晶界上的共晶相增多，共晶相在凝固末期對分離的枝晶起到補(bǔ)縮的作用，導(dǎo)致合金熱裂傾向性減小。研究表明Mg-7Zn-xCu-0.6Zr（x=0，1，2，3）合金微觀裂紋的形成是液膜、凝固收縮補(bǔ)償和晶間搭橋共同作用的結(jié)果。

As one of the highest temperature magnesium alloys, Mg-Zn-Cu ternary alloys are draw much attention in recent years. However, the previous investigations were mainly focused on their microstructure and mechanical properties. The investigations on their solidification and hot tearing behaviors are barely discussed. In order to improve the industrial applications of Mg-Zn-Cu alloy, it is necessary to better understanding of solidification pathways, phase constituent and hot tearing susceptibility (HTS) of these alloys.In this work, the effect of Cu additions on the hot tearing behavious of Mg-7Zn-0.6Zr alloys is studied using with T type hot tearing mold. The microstructure and the morphology of cracking zone of Mg-7Zn-xCu-0.6Zr alloys were observed by X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. The hot cracking susceptibility of Mg-7Zn-xCu-0.6Zr (x=0,1,2,3) alloys were characterized by the measurement of crack volume in this paper. The experimental results shown that the grain sizes of Mg-7Zn-0.6Zr alloys were refined by addition of Cu element. Meanwhile, the amount of eutectic phase was increased with increasing the Cu content and the separated dendritic was refilled by the eutectic phase. The experimental results also shown that hot tearing susceptibility of Mg-7Zn-0.6Zr was decreased with increasing of Cu content. The Mg-7Zn-0.6Zr and Mg-7Zn-1Cu-0.6Zr alloys were completely broken. The hot cracks of Mg-7Zn-xCu-0.6Zr（x=0，1，2，3） alloys were formed by liquid film、solidification shrinkage and interdendritic bridge.

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