高性能VW73B镁合金微观组织与力学性能研究

Study on microstructure and mechanical properties of high performance VW73B magnesium alloy

随着全球节能减排政策的推进,高性能镁合金因其低密度、高比强度、可持续发展等优势在交通运输领域得到了广泛的应用。本文通过OM,SEM和TEM等手段研究了VW73B镁合金铸态、均匀化态、挤压态以及时效态的微观组织与性能。结果表明:铸态合金由α‑Mg、(Mg,Zn)3RE相、Mg5(RE,Zn)相和LPSO相构成,均匀化处理后,合金中仅存在α‑Mg和LPSO结构相。挤压变形后,晶粒显著细化,分布于晶界处的块状LPSO结构相促进了动态再结晶行为的发生。挤压态合金由未发生动态再结晶的粗晶和细小的动态再结晶晶粒组成,LPSO结构相沿挤压方向呈流线分布。峰时效态合金中存在大量纳米级β'沉淀相和细长针状基面层错,其抗拉强度为416 MPa,屈服强度为344 MPa,断后伸长率为10.0%。VW73B合金优异的力学性能是细晶强化、时效强化、块状LPSO结构相以及层片状LPSO结构相共同作用的结果。

With the promotion of global energy conservation and emission reduction policies,high performance magnesium alloys have been widely used in the field of transportation due to their advantages of low density,high specific strength and sustainable development.The microstructure and properties of VW73B magnesium alloy as cast,homogenized,extruded and aged are studied by means of OM,SEM and TEM.The results show that the as-cast alloy is composed ofα-Mg,(Mg,Zn)3RE,Mg5(RE,Zn)and LPSO phases.After homogenization,onlyα-Mg and LPSO phases exist in the alloy.After extrusion deformation,the grain is obviously refined,and the block-shaped LPSO structural phase distributed at the grain boundary promotes the dynamic recrystallization behavior.The extruded alloy is composed of coarse grains without dynamic recrystallization and fine dynamic recrystallization grains,and the phase of LPSO structure is distributed in streamline along the extrusion direction.There are a large number of nanoscaleβ'precipitated phases and elongated needle-like base layer faults in the peak-aging alloy.The UTS is 416 MPa,the YS is 344 MPa,and the EL is 10.0%.The excellent mechanical properties of VW73B alloy are the result of the combination of fine crystal strengthening,aging strengthening,bulk LPSO structure phase and lamellar LPSO structure.