In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy
In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy
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DOI：
10.1007/s10853-014-8812-0
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发表时间：
2015-01
影响因子：
4.5
通讯作者：
M. Gzyl;R. Pesci;A. Rosochowski;S. Boczkal;L. Olejnik
中科院分区：
文献类型：
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作者：
M. Gzyl;R. Pesci;A. Rosochowski;S. Boczkal;L. Olejnik
采用扫描电镜原位观察的方法，研究了孪生对AZ 31 B镁合金拉伸过程中应变硬化速率和断裂机制的影响。本研究中使用的三种类型的样品通过（1）挤压（如供应），（2）I-ECAP和（3）I-ECAP后侧镦获得。在每个加工步骤后检查显微组织、织构和机械性能。用一个解析方程来描述试样的流变应力曲线，这些试样表现出各种变形模式：（1）仅由滑移，（2）由拉伸孪晶主导的滑移和（3）由收缩孪晶主导的滑移。结果表明，拉伸孪晶增加应变硬化率，而观察到相反的收缩孪晶。在这项工作中，使用建模方法确定的拉伸和收缩孪晶变形的体积中的滑移的有效施密德因子分别为0.215和0.45。收缩孪晶也被发现是负责早期断裂的挤压样品进行拉伸，因为微裂纹被明确地显示为在孪晶内启动。
The influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy was studied in this work by in situ microstructural analysis during tensile testing in a chamber of scanning electron microscope. Three types of samples used in this study were obtained by (1) extrusion (as-supplied), (2) I-ECAP and (3) I-ECAP followed by side upsetting. Microstructures, textures and mechanical properties were examined after each processing step. An analytical equation was used to describe flow stress curves of the samples which exhibited various modes of deformation (1) only by slip, (2) dominated by tensile twinning followed by slip and (3) dominated by contraction twinning followed by slip. It was shown that tensile twinning increases strain hardening rate, while the opposite is observed for contraction twinning. The effective Schmid factors for slip in volumes deformed by tensile and contraction twinning were determined in this work using modelling approach as 0.215 and 0.45, respectively. Contraction twinning was also revealed to be responsible for an earlier fracture of the extruded sample subjected to tension, since microcracking was shown explicitly to be initiated within twins.