Bi对AZ80镁合金凝固行为及显微组织的影响

来源期刊：金属学报2011年第4期

论文作者：王亚霄 付俊伟 王晶 罗天骄 董旭光 杨院生

文章页码：410 - 416

关键词：AZ80镁合金； Bi； 凝固序列； 共晶转变

Key words：AZ80 magnesium alloy； Bi； solidification procedure； eutectic transformation

摘    要：采用加热-激冷方法和OM,SEM,XRD,DSC等分析手段,研究了AZ80-Bi镁合金的凝固行为,分析了合金的凝固组织特征及其演变过程,阐明了合金的凝固序列.AZ80-2%Bi(质量分数)合金的铸态显微组织由α-Mg,β-Mg₁₇Al₁₂和Mg₃Bi₂相组成,其中Mg₃Bi₂相以片状和颗粒状两种形态存在.将2%Bi加入AZ80合金后,影响了合金的凝固序列,二元共晶转变L→α-Mg+β-Mg₁₇Al₁₂(437℃)被三元共晶转变L→α-Mg+β-Mg₁₇Al₁₂+Mg₃Bi₂(435℃)代替.2%Bi的加入使AZ80合金的初晶形核温度由568.8℃降低至562.6℃,共晶平台温度由424.2℃降到421.1℃.

Abstract: The solidification behavior and as-cast microstructure in AZ80-Bi magnesium alloy were analysed by OM,SEM,XRD and DSC.Meanwhile,the evolution of the solidification microstructure of AZ80-2%Bi alloy was studied by heating-quenching experiments.The results show that the as-cast microstructure of AZ80-2%Bi consists of primary α-Mg matrix,divorced eutectic β-Mg₁₇Al₁₂ phase and Mg₃Bi₂ phase.The Mg₃Bi₂ phase exists in the flake-like and granule-like morphologies. With 2.0%Bi addition,the solidification procedure of AZ80 magnesium alloy is changed.The ternary eutectic transformation L→α-Mg+β-Mg₁₇Al₁₂+Mg₃Bi₂ (at 435℃) takes place during solidification of AZ80-2%Bi alloy instead of the binary eutectic transformation L→α-Mg+β-Mg₁₇Al₁₂ (at 437℃) in AZ80 alloy.Comparing with AZ80 alloy,the nucleating temperature of primaryα-Mg in AZ80- 2%Bi alloy is decreased from 568.8℃ to 562.6℃,and the eutectic temperature is also decreased from 424.2℃ to 421.1℃.