初始取向對大應變軋制AZ31鎂合金板材顯微組織和力學性能的影響Effects of initial orientation on microstructure and mechanical properties of AZ31 magnesium alloy sheets fabricated by large strain rolling

采用大應變軋制技術對軋制面與擠壓板材ED-TE面分別成90°、45°和0°的AZ31鎂合金板材進行加工，研究初始取向對板材顯微組織和力學性能的影響。結果表明：孿生誘發動態再結晶是大應變軋制過程中主要的再結晶機制，動態再結晶的發生使合金晶粒細化、力學性能大幅提高。軋制過程中孿生與板材初始取向密切相關，通過改變初始取向可控制板材晶粒細化和強度改善效果。0°軋制試樣大應變軋制過程中，大部分晶粒的c軸受壓，基面滑移啟動難度增加，孿生的作用增強，壓縮孿晶密度增大，進而通過孿生誘發動態再結晶獲得更為細小的再結晶組織和更為優異的力學性能。壓下量為80%時，0°軋制板材的平均晶粒尺寸為5 μm，抗拉強度、屈服強度和伸長率分別為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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