Mg-6Gd-Y-0.6Zr的析出行为和力学性能

Precipitation behaviors and mechanical properties of Mg-6Gd-Y-0.6Zr alloy

利用光学显微镜、扫描电镜、X线衍射、透射电镜等手段研究添加1%Y(质量分数,下同)对Mg-6Gd-0.6Zr合金析出行为和力学性能的影响。研究结果表明:添加合金元素Y能大大促进Mg-6Gd合金的时效析出;具有高过饱和度的Mg-6Gd-Y-0.6Zr合金在200℃表现出显著的时效硬化现象;随着时效温度的升高,晶界周围析出相极度粗化并且β′相体积分数降低、分布不均;尤其在250℃峰时效的组织中观察到Mg-6Gd合金所不具备的β′相。200℃时效72 h后,合金获得优异的力学性能,其室温抗拉强度、屈服强度和伸长率分别为354 MPa,292 MPa和9.5%,250℃时抗拉强度、屈服强度和伸长率分别为307 MPa,220 MPa和13.6%。

The effect of 1% Y （mass fraction） addition on the precipitation behaviours and mechanical properties of Mg-6Gd-0.6Zr alloy were investigated by using optical microscope （OM）, scanning electron microscope （SEM）, X-ray diffraction （XRD） and transmission electron microscope （TEM）. The results indicate that Y can greatly promote the aging precipitation of Mg-6Gd alloy; Mg-6Gd-Y-0.6Zr alloy maintaining a considerable supersaturation in matrix exhibits a remarkable age-hardening response at 200 ℃ ; the precipitates near grain boundaries get coarser and the volume fraction and distribution of the β＇ precipitates become less and more nonuniform with the increase of the aging temperature; the β＇ phase not found in the peak-aged Mg-6Gd alloy are observed in the alloy peak aged at 250 ℃. Excellent mechanical properties are obtained for the alloy aged at 200 ℃ for 72 h, whose ultimate tensile strength, tensile yield strength and elongation are 354 MPa, 292 MPa and 9.5%, respectively, at room temperature, and 307 MPa, 220 MPa and 13.6%, respectively, at 250 ℃.