AZ31镁合金高应变速率多向锻造组织演变及力学性能

Microstructure evolution and mechanical properties of AZ31 magnesium alloy fabricated by high strain rate triaxial-forging

采用空气锤对AZ31合金在350℃以Δε=0.22的道次应变量进行1~12道次多向锻造变形,并对其组织和性能进行测试。结果表明：合金高应变速率多向锻造（HSRTF）组织演变分为两个阶段,累积应变∑Δε〈1.32时为晶粒细化阶段,其主要机制为孪晶再结晶;累积应变∑Δε〉1.32时为晶粒长大阶段,其主要机制为热激活长大。利用大量的孪晶对再结晶的促进作用,高应变速率多向锻造工艺可快速生产细晶粒高性能AZ31变形镁合金锭坯,累积应变∑Δε=1.32时,可获得组织均匀、平均晶粒度为7.4μm的锻坯,其抗拉强度、屈服强度和伸长率分别为313 MPa、209 MPa和28.6%。

High strain rate triaxial-forging（HSRTF） of AZ31 magnesium alloy was conducted by the pneumatic power hammer at 350 ℃ with a pass strain of 0.22,and the microstructure and mechanical properties of wrought alloy with the different accumulated strains was studied.The results show that the microstructure evolution is divided into two stages according to the different mechanisms： twin DRX（Dynamic recrystallization） induced grain refinement with the accumulated strain ∑Δε lower than 1.32 and thermal activated grain growth with the accumulated strain ∑Δε higher than 1.32.HSRTF is an efficient technique for the preparation of the fine-grained AZ31 alloys with perfect mechanical properties ascribe to the auxo-action of twins on DRX during high strain rate deformation.And a homogeneous structure with the average grain size of 7.4μm can be obtained with the accumulated strain ∑Δε of 1.32,which has the ultimate tensile strength（UTS）,yield strength（YS） and elongation of 313 MPa,209 MPa and 28.6%,respectively.