多向锻造ZK60镁合金组织和性能的均匀性

Homogeneity of microstructure and mechanical properties of ZK60 magnesium alloys fabricated by high strain rate triaxial-forging

采用空气锤对ZK60镁合金进行多向锻造变形,研究锻坯的组织演变以及组织和性能均匀性。结果表明,锻锤与锻坯之间摩擦力的作用造成不均匀变形,使锻坯芯部的实际变形量大于边部的。累积应变∑Δε=3.3时,锻坯芯部组织为蜂窝状粗大再结晶组织和岛状细小再结晶组织,而边部组织则由蜂窝状粗大再结晶组织和呈岛状分布的孪晶组成;其抗拉强度从边部到芯部逐渐降低,而伸长率则由边部向芯部逐渐升高。锻坯力学性能存在一定的各向异性,但锻坯各方向抗拉强度在310.6-323.9 MPa之间,伸长率在21.9%-29.7%之间,表明该工艺可以有效地避免强烈的各向异性,是制备高性能变形镁合金的理想工艺。

Triaxial-forging of ZK60 magnesium alloy was conducted on air hammer, and the microstructure evolution and the homogeneity of microstructures and properties were investigated. The result show that inhomogeneous deformation is detected in the forged specimen due to the friction between the hammer and specimen, and the actual deformation at the central part of the specimen is extensively larger than that at other part. A mixed structure of honeycomb-like coarse dynamic recrystallization （DRX） grains and island-like ultrafine DRX grains are obtained at the central part of the specimen at accumulated strain∑Δεof 3.3, while the structure at the edge part of the specimen consists of honeycomb-like coarse DRX grains and island-like twins. The ultimate tensile strength （UTS） decreases while the ductility increases from the edge part to centre part of the specimen at∑Δεof 3.3. Mechanical anisotropy is also detected in the forged specimen at ∑Δε of 3.3. However, the UTS and elongations at different directions range in 310.6-323.9 MPa and 21.9%-29.7%, respectively, which indicates that extensive anisotropy can be avoided by high strain rate triaxial forging technique. High strain rate triaxial forging is therefore identified as a potential technique for producing wrought magnesium with excellent mechanical properties.