初始取向对大应变轧制AZ31镁合金板材显微组织和力学性能的影响Effects of initial orientation on microstructure and mechanical properties of AZ31 magnesium alloy sheets fabricated by large strain rolling

采用大应变轧制技术对轧制面与挤压板材ED-TE面分别成90°、45°和0°的AZ31镁合金板材进行加工，研究初始取向对板材显微组织和力学性能的影响。结果表明：孪生诱发动态再结晶是大应变轧制过程中主要的再结晶机制，动态再结晶的发生使合金晶粒细化、力学性能大幅提高。轧制过程中孪生与板材初始取向密切相关，通过改变初始取向可控制板材晶粒细化和强度改善效果。0°轧制试样大应变轧制过程中，大部分晶粒的c轴受压，基面滑移启动难度增加，孪生的作用增强，压缩孪晶密度增大，进而通过孪生诱发动态再结晶获得更为细小的再结晶组织和更为优异的力学性能。压下量为80%时，0°轧制板材的平均晶粒尺寸为5 μm，抗拉强度、屈服强度和伸长率分别为311.4 MPa、202.6 MPa和26.9%。

Large strain rolling was carried out on AZ31 magnesium alloy with different orientations which was machined from an extruded sheet along angles of 90°, 45° and 0° to the ED-TE plane, and the effects of initial orientation on the microstructure and mechanical properties of the sheets were investigated. The result show that twin induced dynamic recrystallization (DRX) is the main DRX mechanism during large strain rolling, which consequently results in the grain refinement and improvement of mechanical properties. Twinning is sensitive to initial orientation during rolling, therefore, the grain refinement and improvement of mechanical properties can be controlled by alternating initial orientation. The basal slip is difficult to activate during large strain rolling of 0° specimen due to the compression stress applied on the c-axis of most grains. Therefore, the role of twinning enhanced, especially compression twinning, consequently results in much finer DRX grains and much better mechanical properties. The average grain size of 0° specimen at rolling reduction of 80% is 5 μm, and the ultimate tensile strength (UTS), yield strength (YS) and elongation of the sheets are 311.4 MPa, 202.6 MPa and 26.9%, respectively.

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