(1. 清华大学 机械工程系, 北京 100084；
2. 清华大学 基础工业训练中心, 北京 100084；
3. 清华大学 工程力学系， 北京 100084)
摘 要: 研究了稀土（0.1%~1.2％）对AZ31B变形镁合金组织和力学性能的影响。 结果表明： 在AZ31B变形镁合金中添加稀土后，晶粒显著粗化， 合金的室温力学性能下降。 晶粒粗化一方面是由于RE与Al结合生成了Al11RE3相， 消耗了一部分铝量， 削弱了铝对α-Mg晶粒的细化作用； 另一方面RE与ε-AlMn相反应生成Al-RE-Mn相， 使得合金熔体中的异质形核核心减少；稀土引起AZ31B变形镁合金晶粒粗化在热分析曲线上表现为初晶形核最低温度从628.8下降到626.3 ℃， 初晶再辉温差从0.8 ℃上升到3.2 ℃。
关键字: AZ31B变形镁合金； 稀土； 晶粒尺寸； 热分析； 力学性能
mechanical properties of AZ31B wrought magnesium alloy
（ 1. Department of Mechanical Engineering, Tsinghua University,
Beijing 100084, China；
2. Fundamental Industry Training Center, Tsinghua University,
Beijing 100084, China;
3. Department of Engineering Mechanics, Tsinghua University,
Beijing 100084, China ）
Abstract: The effects of rare earth on the microstructure and mechanical properties of AZ31B wrought magnesium alloy were investigated. The results show that when adding rare earth into AZ31B wrought magnesium alloy, the grains are coarsened remarkably, as a result the mechanical properties decline. The causes for the grain coarsening are as follows: RE reacts with Al to form Al11RE3 phases, consumes a part of Al atoms, and weakens the grain refinement effect of Al on the α-Mg grains. RE reacts with ε-AlMn phases to form Al-RE-Mn compounds, thus reducing the amounts of heterogeneous nuclei in the melt. As a result of the grain coarsening of AZ31B wrought magnesium alloy by rare earth, the lowest temperature for primary phase nucleation decreases from 628.8 ℃ to 626.3 ℃ and the temperature difference of recalescence increases from 0.8 ℃ to 3.2 ℃.
Key words: AZ31B wrought magnesium alloy; rare earth; grain size; thermal analysis; mechanical property
