多向鍛造ZK60鎂合金組織和性能的均勻性Homogeneity of microstructure and mechanical properties of ZK60 magnesium alloys fabricated by high strain rate triaxial-forging

采用空氣錘對ZK60鎂合金進行多向鍛造變形，研究鍛坯的組織演變以及組織和性能均勻性。結(jié)果表明，鍛錘與鍛坯之間摩擦力的作用造成不均勻變形，使鍛坯芯部的實際變形量大于邊部的。累積應(yīng)變∑Δε=3.3時，鍛坯芯部組織為蜂窩狀粗大再結(jié)晶組織和島狀細(xì)小再結(jié)晶組織，而邊部組織則由蜂窩狀粗大再結(jié)晶組織和呈島狀分布的孿晶組成；其抗拉強度從邊部到芯部逐漸降低，而伸長率則由邊部向芯部逐漸升高。鍛坯力學(xué)性能存在一定的各向異性，但鍛坯各方向抗拉強度在310.6~323.9 MPa之間，伸長率在21.9%~29.7%之間，表明該工藝可以有效地避免強烈的各向異性，是制備高性能變形鎂合金的理想工藝。

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 ∑Δε of 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 ∑Δε of 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.

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