(1. 湖南科技大學(xué) 材料科學(xué)與工程學(xué)院，湘潭 411201；
2. 湖南科技大學(xué) 湖南省新能源汽車產(chǎn)學(xué)研海智創(chuàng)新中心，湘潭 411201；
3. 湖南工程學(xué)院 湖南省汽車動力與傳動系統(tǒng)重點(diǎn)實(shí)驗(yàn)室，湘潭 411104)
摘 要: 本文提出了膨脹-連續(xù)剪切變形的新方法，利用光學(xué)顯微鏡和電子背散射衍射技術(shù)(EBSD)研究了膨脹-連續(xù)剪切變形AZ31鎂合金的晶粒細(xì)化機(jī)理。結(jié)果表明：AZ31鎂合金經(jīng)變形后晶粒尺寸由150 μm細(xì)化至約2.5 μm。在膨脹變形過程中， 拉伸孿晶是主要的變形機(jī)制，其孿晶界為動態(tài)再結(jié)晶提供大量的形核位置，促進(jìn)了動態(tài)再結(jié)晶的發(fā)生；在開口位置處，鎂合金經(jīng)歷了大的擠壓比和剪切變形，柱面 滑移被激活，在基面和柱面 滑移共同作用下進(jìn)一步均勻細(xì)化晶粒組織。在整個變形過程中，小角度晶界逐漸轉(zhuǎn)變?yōu)榇蠼嵌染Ы纾蠼嵌染Ы绾坑蓴D壓通道處的27.6%增加到板材成形通道處的72.2%，動態(tài)再結(jié)晶發(fā)生程度更加充分。AZ31鎂合金的晶粒細(xì)化主要是孿晶誘發(fā)的動態(tài)再結(jié)晶和連續(xù)動態(tài)再結(jié)晶共同作用所致。
關(guān)鍵字: AZ31鎂合金；膨脹-連續(xù)剪切變形；動態(tài)再結(jié)晶；晶粒細(xì)化
（1. School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China;
2. Hunan Provincial Overseas-wisdom Innovation Center of New Energy Vehicle in Industrial-Academic-Research Cooperation, Hunan University of Science and Technology, Xiangtan 411201, China;
3. Hunan Provincial Key Laboratory of Vehicle Power and Transmission System, Hunan Institute of Engineering, Xiangtan 411104, China）
Abstract:This study proposes a new method of expansion-continuous shear deformation, and the grain refinement mechanism of AZ31 alloy was investigated with an optical microscopy and electron backscatter diffraction. Results show that AZ31 alloy can refine the grains from 150 μm to about 2.5 μm. During the expansion deformation, tensile twinning is the main deformation mechanism, which can offer numerous nucleation sites to trigger dynamic recrystallization. At the opening position, the Mg alloys have undergone large extrusion-ratio and shearing deformation, which can activation of prismatic slip. Grains refinement and uniform microstructure are improved due to the basal and prismatic slip. During the whole process, low-angle grain boundaries are gradually transformed into high-angle grain boundaries. Dynamic recrystallization becomes more sufficient due to the content of high-angle grain boundaries increasing from 27.6% at the position of the extrusion channel to 72.2% at the position of the channel of sheet forming. Therefore, the grain refinement mechanisms of Mg alloys are dynamic recrystallization stimulated by twinning and continuous dynamic recrystallization.
Key words: AZ31 magnesium alloy; expansion-continuous shear deformation; dynamic recrystallization; grain refinement
