铒和钕对铸态ZK60镁合金显微组织和力学性能的影响

Effect of Erbium and Neodymium on Microstructure and Mechanical Properties of ZK60 Magnesium Alloy

研究了铒和钕对铸态ZK60镁合金显微组织和力学性能的影响。结果表明:ZK60镁合金中添加Er或Nd能够细化晶粒,改变合金的显微组织。当ZK60镁合金中加入1.0%(质量分数)的Er或Nd具有最佳的细化效果,与原ZK60镁合金晶粒尺寸相比较,晶粒的平均直径由原来的33.0μm分别减少至23.6和25.2μm。添加Er或Nd的ZK60镁合金形成含有Er或Nd的稀土共晶相,其熔点为518℃。稀土共晶相对晶粒具有钉扎作用,提高合金在150℃时的抗拉强度。稀土共晶相的形态和分布对室温力学性能有显著影响。含有Er的共晶相析出数量较少,沿晶界不连续分布,提高合金室温强度的同时塑性略有改善,而含有Nd的共晶相形态粗大,析出数量较多,沿晶界网状连续分布,合金固溶强化效果明显减弱,室温强度和塑性均降低。

Effect of Er and Nd on the microstructure and mechanical properties of ZK60 magnesium alloy was studied. The results show that the refined and modified microstructure of ZK60 magnesium alloy is made by the addition of Er or Nd. The optimal refined effect is obtained by the addition of 1.0% （mass fraction） Er or Nd, and the grain size is reduced from 33.0 to 23.6 and 25.2 μm, respectively. The rare earth （RE） eutectic phase （ternary Mg-Zn-Er or Mg- Zn-Nd phase） is formed by the addition of Er or Nd. The melting points of the two kinds of RE eutectic phase are both at 518 ℃. The RE eutectic phases both have good stability at elevated temperature,which can pin grains and markedly improve the tensile strength of the alloy at elevated temperature. The morphologies and distribution of RE eutectic phases have marked effect on the tensile properties of the alloy at room temperature. The Mg-Zn-Er phase is irregularly and discontinuously formed along grain boundaries, which can improve the tensile strength and elongation of the alloy. The Mg-Zn-Nd eutectic phase is bulky and net-liked, continuously distributed along grain boundaries, which weakens the effect of solid solution strengthening of Zn in matrix, can decrease the tensile strength and deteriorate plasticity of the alloy.