Effect of twinning on the deformation behavior of an extruded Mg–Zn–Zr alloy during hot compression testing
Effect of twinning on the deformation behavior of an extruded Mg–Zn–Zr alloy during hot compression testing
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DOI：
10.1016/j.msea.2012.06.101
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发表时间：
2012-10
期刊：
影响因子：
6.4
通讯作者：
W. Ai;G. Fang;J. Zhou;M. Leeflang;J. Duszczyk
中科院分区：
文献类型：
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作者：
W. Ai;G. Fang;J. Zhou;M. Leeflang;J. Duszczyk
研究了变形镁合金热变形过程中孪晶的形成和演化，以及孪晶对应变硬化的影响。对挤压后的Mg-Zn-Zr合金进行了热压缩试验，温度为350 ~ 450℃，应变速率为0.01 ~ 10s−1。当Zener-Hollomon参数值较大时，应力-应变曲线呈凹形。然而，在Z参数较低的情况下，在试验中没有观察到这种应力-应变曲线形状。对高Z参数下的断续压缩试样的显微组织分析表明，当变形材料处于加工硬化状态时，大量的延伸孪晶形成并达到饱和。在每个拉长的晶粒中，大多数孪晶是彼此平行的。当延伸孪晶完全消耗掉拉长的晶粒基体后，出现了大量的收缩孪晶，通过Hall-Petch效应导致应变硬化速率增加，变形达到稳态后最终形成项链状组织。而在较低的Z参数下，孪晶的形成和演化几乎不发生，压缩后形成均匀的等轴组织。
The research was aimed to understand the formation and evolution of twins during hot deformation of a wrought magnesium alloy and the effect of twinning on strain hardening. Hot compression tests of an extruded Mg–Zn–Zr alloy were performed at temperatures of 350–450°C and strain rates of 0.01–10s−1. A concave stress–strain curve shape was observed, when a high value of the Zener–Hollomon parameter was applied. Such a stress–strain curve shape was however not observable during tests at a low value of the Z parameter. Microstructure examination of specimens obtained from interrupted compression tests at high values of the Z parameter showed that a large number of the extension twins formed and then reached saturation when the deforming material was in the work-hardening regime. Most of these twins in each elongated grain were found to be parallel to each other. After the extension twins completely consumed the elongated grain matrix, a number of contraction twins emerged, leading to an increased strain-hardening rate through the Hall–Petch effect and finally to a necklace-like microstructure after deformation reached the steady state. However, at low values of the Z parameter, the formation and evolution of twins hardly occurred, leading to a uniform equiaxial grain structure after the compression tests.