电弧增材制造Mg-4Y-3Nd-0.5Zr合金微观组织与力学性能

Microstructure and Mechanical Properties of Mg-4Y-3Nd-0.5Zr Alloy Fabricated by Wire Arc Additive Manufacturing

摘要:

采用电弧增材制造技术制备了WE43（Mg-4Y-3Nd-0.5Zr，质量分数，%）镁稀土合金单壁墙构件，并通过多尺度组织表征、显微硬度和拉伸测试等手段系统研究了沉积态WE43合金的微观组织及其力学性能。此外，对比研究了直接时效处理（T5）和固溶+时效处理（T6）对微观组织演化行为和力学性能的影响。结果表明，沉积态WE43合金为均匀全等轴晶组织，平均晶粒尺寸为25.3 μm，晶界处存在网状共晶组织（α-Mg+Mg₄₁Nd₅/Mg₂₄Y₅），沉积态合金的抗拉强度可达到190 MPa。经T5处理后，峰值时效硬度由沉积态的74 HV_0.2提升至91 HV_0.2，基体中存在大量残留共晶组织。T6热处理可获得更高的峰值时效硬度（108 HV_0.2），共晶组织充分回溶，基体中残留少量的Mg₂₄Y₅相。T6处理使得合金抗拉强度提升至283 MPa，但也容易引发明显的晶粒异常长大现象，且沿竖直方向的延伸率显著低于水平方向。

关键词:电弧增材制造;镁稀土合金;微观组织;热处理;力学性能

Abstract:

A WE43 (Mg-4Y-3Nd-0.5Zr, wt%) magnesium-rare earth alloy thin-wall component was fabricated by wire arc additive manufacturing, and its microstructure and mechanical properties were investigated by multiscale characterization, microhardness, and tensile tests. The influences of direct aging (T5) and solid solution+aging (T6) on the microstructure evolution and mechanical properties were studied. Results indicate that the as-deposited WE43 alloy has a uniform equiaxed crystal matrix, with an average grain size of 25.3 μm. Reticulated eutectic structure (α-Mg+Mg₄₁Nd₅/Mg₂₄Y₅) is formed due to Nd and Y element liquid segregation at grain boundaries. Tensile strength of as-deposited alloys is 190 MPa. Peak hardness increases from 74 HV_0.2 to 91 HV_0.2 after T5 aging with persistence of significant eutectic structures. Peak aging hardness is 108 HV_0.2 after T6 treatment, and the eutectic structure is dissolved completely, while a small amount of Mg₂₄Y₅ remains in matrix. Tensile strength of alloys is enhanced to 283 MPa after T6 treatment, but it also induces significant grain growth and reduces the elongation in vertical direction more obviously than in horizontal direction.

Key words:wire arc additive manufacturing;magnesium-rare earth alloys;microstructure;heat treatment;mechanical properties