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摘要：
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利用OM、SEM和EDS研究稀土元素Pr变质对AZ91镁合金的微观组织的影响，并探究其与合金显微组织及力学性能的关系。结果表明，随着稀土元素Pr含量的增加，粗大树枝状的β-Mg17Al12相开始断裂，尺寸逐渐减小。当Pr添加量（质量分数）为1.0%时，粗大树枝状的β-Mg17Al12相断裂为短棒状。然而，当Pr含量继续增加时，β-Mg17Al12相尺寸又开始变大。随着Pr的添加，合金中生成条状Al11Pr3相和块状Al6Mn6Pr相。热挤压可以显著细化铸态AZ91镁合金晶粒，挤压后，β-Mg17Al12相沿挤压方向有序排列。随着Pr含量的增加，挤压态AZ91镁合金的力学性能呈现先上升后下降的趋势。当稀土元素Pr添加量为1.0%时，AZ91镁合金力学性能最佳，合金抗拉强度、伸长率、硬度较基体分别提升了20.5%，26.0%和18.5%。
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The influence of rare earth element Pr on the microstructure and mechanical properties of magnesium alloy AZ91 was investigated by OM, SEM and EDS, and the relationship between the microstructure and mechanical properties of magnesium alloy AZ91 was discussed. The results show that with increasing of Pr content, coarse dendritic β-Mg17Al12 phase begins to break, and the size becomes smaller gradually. When Pr content is up to 1.0% (mass fraction), the shape of coarse dendritic β-Mg17Al12 phase changes into short rod. However, when Pr content increases continually, the size of β-Mg17Al12 phase increases again, and stripe Al11Pr3 phase and globular Al6Mn6Pr phase form in the alloy. Thus, hot extrusion can significantly reduce the grain size of as-cast magnesium alloy AZ91, and β-Mg17Al12 phase arranges orderly along the extrusion direction after extrusion. With the increase of Pr content, mechanical properties of as-extrusion magnesium alloy AZ91 firstly decrease and then increase. When Pr content is up to 1.0%, the mechanical properties reach optimum, and the tensile strength, elongation and hardness of the as-extruded AZ91 are increased by 20.5%, 26.0% and 18.5%, respectively.
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基金项目：
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江西省自然科学基金资助项目 (20171BAB206034)
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作者简介：
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作者简介：吴烁（1992-），男，硕士研究生
E-mail：wushuo199201@163.com
通讯作者：闫洪（1962-），男，博士，教授，博士生导师
E-mail：yanhong_wh@163.com
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