重力铸造Mg-3Nd-0.2Zn-Zr镁合金高周疲劳行为的研究

Study on High Cycle Fatigue Behavior of Gravity Cast Mg-3Nd-0.2Zn-Zr Magnesium Alloy

摘要:

对重力金属型铸造 (GPC) 和重力砂型铸造(GSC)Mg-3Nd-0.2Zn-Zr(NZ30K) (质量分数，%)合金T6态的显微组织、室温拉伸性能和室温拉压疲劳性能 (R= –1) 进行对比研究。研究发现，GPC-NZ30K合金晶粒大体呈正态分布，平均晶粒较细小 (60 μm)；GSC-NZ30K合金晶粒分布偏离正态分布，晶粒尺寸大小不均匀且平均晶粒较粗大 (70 μm)。晶粒细小均匀的显微组织 (GPC-NZ30K-T6合金) 可以明显提高合金的室温拉伸性能，包括屈服强度 (+6.6 MPa)、抗拉强度 (+43 MPa)和延伸率 (+2.8%)，但对于提高合金的室温拉压疲劳强度 (+1.12 MPa) 作用不明显；平均晶粒略粗大且大小分布不均匀的显微组织 (GSC-NZ30K-T6合金) 可使NZ30K-T6合金的疲劳性能稳定。

Abstract:

The optical microstructure, mechanical properties and high cycle tension-compression fatigue properties (R= –1) at room temperature of gravity permanent cast (GPC) and gravity sand cast (GSC) Mg-3Nd-0.2Zn-Zr (NZ30K) (wt.%) magnesium alloy were studied. Results show that GPC-NZ30K alloy has normal grain size distribution generally, with relatively fine grains, about 60 μm, while GSC-NZ30K alloy has non-uniform grain size distribution, with relatively coarse grains, about 70 μm. Finer grains in GPC-NZ30K-T6 alloy lead to higher yield strength (+6.6 MPa), higher ultimate tensile strength (+43 MPa) and higher elongation (+2.8%). However, it has a little influence on fatigue strength (+1.12 MPa). Coarse and non-uniform grain size distribution in GSC-NZ30K-T6 alloy is favor to minimize the fatigue variation of cast NZ30K-T6 alloy.