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利用SEM和XRD等方法研究了总添加量为2.5%(质量分数,下同)的单加或复合添加La和Nd的AZ91镁合金的铸态显微组织和相组成,并测试和分析了合金的室温力学性能。结果表明:单加或复合添加2.5%的La和Nd使AZ91合金中的β相Mg17Al12数量明显减少。单加La和单加Nd在AZ91合金中形成的稀土相分别是针状的Al11La3和块状的Al2Nd;二者复合加入时两种稀土相同时出现,Al11La3相和Al2Nd相的尺寸较单加时有所减小,其相对含量与两种稀土元素添加量成正比。当复合添加La和Nd时,Al11La3相中的部分La和Al2Nd相中的部分Nd分别被Nd和La置换。相对于单一添加,复合添加La和Nd能更显著地改善AZ91的力学性能。本实验研究的合金中,AZ91+1.0%La+1.5%Nd合金力学性能最好,其铸态合金的抗拉强度和延伸率分别为235MPa和10%。
The as-cast microstructure and phase composition of AZ91 magnesium alloy with addition of La and Nd alone or in combination with 2.5% (mass fraction, the same below) were studied by SEM and XRD. The alloy Room temperature mechanical properties. The results show that the amount of β phase Mg17Al12 in AZ91 alloy decreases obviously when 2.5% La or Nd is added alone or in combination. The rare earth phases formed by AZ91 alloy with La alone and Nd alone are acicular Al11La3 and massive Al2Nd, respectively. When the two rare earths are the same, the sizes of Al11La3 phase and Al2Nd phase are longer than that of Al2Nd phase alone Has been reduced, the relative content of two rare earth elements is proportional to the amount added. When La and Nd were added in combination, part of La in the Al11La3 phase and part of Nd in the Al2Nd phase were replaced by Nd and La, respectively. Compared with a single addition, the compound addition of La and Nd can improve the mechanical properties of AZ91 more significantly. The alloys AZ91 + 1.0% La + 1.5% Nd have the best mechanical properties, and the tensile strength and elongation of as-cast alloys are 235MPa and 10% respectively.