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采用硬度测试、室温拉伸、X射线衍射、扫描电镜和透射电镜等研究了Gd元素含量对Mg-Gd-Y-Nd-Zr合金微观组织和力学性能的影响。结果表明:铸态Mg-xGd-3.0Y-1.0Nd-1.0Zr(x=5.0、5.5、6.0)合金的相组成均为镁基体及非平衡共晶Mg_(5.05)RE(RE=Gd、Y、Nd),非平衡共晶的化学成分对Gd元素含量不敏感,但体积分数随Gd含量的增加而增加。经固溶处理后,非平衡共晶均可溶入镁基体,但在晶界残留富稀土粒子。当Gd含量超过5.5wt%后,晶界上的富稀土粒子开始团聚,降低合金的力学性能。经成分优化,较优的合金成分为Mg-5.5Gd-3.0Y-1.0Nd-1.0Zr,其铸造-T6态的抗拉强度为322 MPa,伸长率为4.0%,力学性能优于总稀土含量与之相当的商用WE54合金。
The effects of Gd content on the microstructure and mechanical properties of Mg-Gd-Y-Nd-Zr alloy were investigated by hardness test, tensile test at room temperature, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show that the phase compositions of as-cast Mg-xGd-3.0Y-1.0Nd-1.0Zr (x = 5.0,5.5,6.0) alloy are Mg matrix and non-equilibrium eutectic Mg 5.05 RE (RE = Gd, Y , Nd). The chemical composition of non-equilibrium eutectic is not sensitive to the content of Gd, but the volume fraction increases with the increase of Gd content. After solution treatment, non-equilibrium eutectic can be dissolved into the magnesium matrix, but rich in rare earth particles remain in the grain boundary. When the Gd content exceeds 5.5wt%, the grain boundary rich in rare earth particles began to agglomerate, reducing the mechanical properties of the alloy. The optimized alloy composition is Mg-5.5Gd-3.0Y-1.0Nd-1.0Zr. The tensile strength of casting -T6 state is 322 MPa, the elongation is 4.0%, and the mechanical properties are better than the total rare earth Equivalent content of commercial WE54 alloy.