Strain-induced selective grain growth in AZ31 Mg alloy sheet deformed by equal channel angular pressing
Strain-induced selective grain growth in AZ31 Mg alloy sheet deformed by equal channel angular pressing
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DOI：
10.1016/j.matchar.2016.01.002
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发表时间：
2016-03-01
影响因子：
4.7
通讯作者：
Letzig, D.
中科院分区：
文献类型：
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作者：
Victoria-Hernandez, J.;Suh, J.;Letzig, D.
研究了等通道转角挤压（ECAP）AZ 31镁合金板材退火过程中的显微组织变化。尺寸为200 x 200 x 1.8 mm（3）的样品在225 ℃下使用130度的通道角在单次ECAP过程中进行处理。随后的等温和等时热处理用于揭示ECAP片材在180和300摄氏度之间的温度下的微观结构稳定性。利用光学显微镜和电子背散射衍射（EBSD）的微观结构的发展进行了系统的分析。结果表明，由于热退孪晶，ECAP过程中{1012}延伸孪晶的大量激活所产生的织构改变在退火过程中消失。此外，在250 ℃和300 ℃下观察到由小晶粒和粗晶粒组成的双峰显微组织，这是由于少数晶粒的快速生长。这种选择性晶粒长大的原因与ECAP处理后的板材中所包含的大的存储应变所激发的应变诱导晶界迁移的激活有关。Mg（17）A（12）颗粒在退火过程中的溶解也被视为快速晶粒生长开始的可能因素。(C)2016 Elsevier Inc. All rights reserved.
In this work the microstructure development during annealing of AZ31 sheets processed by equal channel angular pressing (ECAP) is presented. Samples with dimensions of 200 x 200 x 1.8 mm(3) were processed in a single ECAP pass at 225 degrees C using a channel angle of 130 degrees. Subsequent isothermal and isochronal heat treatments were used to reveal the microstructure stability of the ECAPed sheets at temperatures between 180 and 300 degrees C. A systematic analysis of the microstructure development was conducted using optical microscopy and electron backscatter diffraction (EBSD). It was found that a texture modification produced by the profuse activation of {1012} extension twinning during ECAP is lost during annealing as a result of thermal detwinning. Moreover, a bimodal microstructure composed by small and coarse grains was observed at 250 degrees C and 300 degrees C as a result of the fast growth of a few grains. The reason for the selective grain growth is related with the activation of strain induced grain boundary migration which was stimulated by the large stored strain contained in the as-ECAP processed sheets. The dissolution of Mg(17)A(12) particles during annealing is also seen as a possible factor for the onset of rapid grain growth. (C) 2016 Elsevier Inc. All rights reserved.