Zn添加对铸造Mg-Gd-Y-Zr合金组织和力学性能的影响

摘要

研究Zn添加对Mg-10Gd-3Y-0.6Zr(wt.％)合金在铸态、固溶态和峰时效态下显微组织和力学性能的影响.实验结果表明,不含Zn的铸态合金由α-Mg和Mg24(Gd,Y)5相组成,而含0.5 wt.％Zn的铸态合金由α-Mg、(Mg,Zn)3(Gd,Y)和Mg24(Gd,Y,Zn)5相组成.随着Zn含量增加到1 wt.％,Mg24(Gd,Y,Zn)5相消失,一些针状堆垛层错沿晶界分布.此外,在含2 wt.％Zn的铸态合金中观察到18R型长周期结构相.固溶处理后,Mg24(Gd,Y)5和Mg24(Gd,Y,Zn)5共晶相完全溶解,(Mg,Zn)3(Gd,Y)相、针状堆垛层错和18R型长周期结构相均转化为14H型长周期结构相.适当体积分数的14H型长周期结构相和细小的椭球状β′相共同赋予峰时效态下含0.5 wt.％Zn合金优良的综合力学性能,该合金的抗拉强度、屈服强度和伸长率分别为338 MPa、201 MPa和6.8％.%The effects of Zn addition on the microstructure and mechanical properties of Mg-10Gd-3Y-0.6Zr (wt.％) alloys in the as-cast, solution-treated, and peak-aged conditions were investigated. Experimental results reveal that the microstructure of the as-cast alloy without Zn consists ofα-Mg and Mg24(Gd,Y)5 phases, and the alloy with 0.5 wt.％Zn consists ofα-Mg, (Mg,Zn)3(Gd,Y) and Mg24(Gd,Y,Zn)5 phases. With the addition of Zn increasing to 1 wt.％, the Mg24(Gd,Y,Zn)5 phase disappears and some needle-like stacking faults distribute along the grain boundaries. Moreover, the 18R long-period stacking ordered (LPSO) phase is observed in the as-cast alloy with 2 wt.％ Zn. After solution treatment, the Mg24(Gd,Y)5 and Mg24(Gd,Y,Zn)5 eutectic phases are completely dissolved, and the (Mg,Zn)3(Gd,Y) phase, needle-like stacking faults and 18R LPSO phase all transform into 14H LPSO phase. Both the suitable volume fraction of 14H LPSO phases and the fine ellipsoidal-shaped β′ phases make the peak-aged alloy with 0.5 wt.％Zn exhibit excellent comprehensive mechanical properties and the UTS, YS and elongation are 338 MPa, 201 MPa and 6.8％, respectively.