初始取向?qū)Υ髴?yīng)變軋制AZ31鎂合金板材顯微組織和力學(xué)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(yīng)變軋制技術(shù)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(jìn)行加工，研究初始取向?qū)Π宀娘@微組織和力學(xué)性能的影響。結(jié)果表明：孿生誘發(fā)動(dòng)態(tài)再結(jié)晶是大應(yīng)變軋制過程中主要的再結(jié)晶機(jī)制，動(dòng)態(tài)再結(jié)晶的發(fā)生使合金晶粒細(xì)化、力學(xué)性能大幅提高。軋制過程中孿生與板材初始取向密切相關(guān)，通過改變初始取向可控制板材晶粒細(xì)化和強(qiáng)度改善效果。0°軋制試樣大應(yīng)變軋制過程中，大部分晶粒的c軸受壓，基面滑移啟動(dòng)難度增加，孿生的作用增強(qiáng)，壓縮孿晶密度增大，進(jìn)而通過孿生誘發(fā)動(dòng)態(tài)再結(jié)晶獲得更為細(xì)小的再結(jié)晶組織和更為優(yōu)異的力學(xué)性能。壓下量為80%時(shí)，0°軋制板材的平均晶粒尺寸為5 μm，抗拉強(qiáng)度、屈服強(qiáng)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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