多向锻造及时效对Mg-Gd-Y-Zr组织和力学性能的影响

Effect of multidirectional forging and ageing treatment on microstructure and mechanical properties of Mg-Gd-Y-Zr alloy

利用光学显微观察(OM)、透射电子显微分析(TEM)、维氏硬度及力学性能测试等手段,研究多向锻造及时效对Mg-Gd-Y-Zr合金组织及力学性能的影响。结果表明:在1~6道次锻造变形中,随着变形道次的增加,晶粒不断细化;在6道次变形(∑ε=4.2)后样品获得最细的晶粒组织,其平均晶粒尺寸约为7.5μm;对6道次变形样品进行200℃×42 h的峰值时效处理,在晶粒内部分解出细小致密的β′相;样品经锻造后,综合力学性能较均匀化态有显著提高,且随变形道次的增加而不断增加;时效处理使材料的强度获得进一步提升,而伸长率则有所下降;其中,6道次变形样品的变形态、时效态的屈服强度、抗拉强度、伸长率分别为213、312 MPa,10.9%,327、435 MPa,3.0%。变形态样品综合力学性能的逐步提高主要归功于晶粒的不断细化,而时效态样品强度的提升以及伸长率的下降则与β′相的产生密切相关。

The effect of multidirectional forging（MDF）and ageing treatment on microstructure and mechanical properties of MgGd-Y-Zr alloy was investigated by using OM,TEM,Vickers hardness tester and mechanical property test instrument. Results show that with increasing forging passes from one to six,the average grain size decreases gradually and the grains as fine as 7.5μm are achieved after six passes forging. After peak-ageing at 200 ℃ for 42 h,fine and dense β′ phase appears in the grains of sample forged by six passes. The comprehensive mechanical properties of the as-forged samples experience a remarkable increase compared to those of as-homogenized samples and keep increasing with increasing forging passes. A further increase in strength but a decline in elongation is realized by the ageing treatment. The YS,UTS and elongation under as-forged and as-aged conditions of sample forged by six are 213 MPa,312 MPa,10.9% and 327 MPa,435 MPa,3.0%,respectively. The gradual increase in comprehensive mechanical properties of as-forged samples is mainly attributed to the continuous refinement of grains,while the change in mechanical properties of peak-aged sample is closely related to the precipitation of β′ phase.