Dependence of the distribution of deformation twins on strain amplitudes in an extruded magnesium alloy after cyclic deformation
Dependence of the distribution of deformation twins on strain amplitudes in an extruded magnesium alloy after cyclic deformation
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DOI：
10.1016/j.msea.2009.04.048
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发表时间：
2009-08
期刊：
影响因子：
6.4
通讯作者：
C. Fan;D. Chen;A. Luo
中科院分区：
文献类型：
--
作者：
C. Fan;D. Chen;A. Luo
研究了新型镁合金AM30在应变控制低周疲劳试验后沿挤压方向加载方向的循环变形特征和变形孪晶的分布。在0.2%的低应变幅值、低应力幅值和小的塑性应变幅值下，合金表现出基本的循环稳定性，而在0.6%的高应变幅值下表现出较强的循环硬化。在较高的应变幅值下循环变形时，除了初始的高应力幅值和大的塑性应变幅值外，随着循环变形的进行，应力幅值显著增大，塑性应变幅值显著降低。压缩孪晶和拉伸去孪晶在两种应变幅值下都发生，断口附近观察到的残余孪晶分布是孪晶和去孪晶竞争的结果，这取决于应变幅值、循环硬化-软化特性和裂纹尖端前方的塑性区尺寸。在低应变幅值的稳定循环变形中，变形孪晶主要出现在最终快速断裂之前的区域，而在高应变幅值循环硬化时，变形孪晶主要出现在裂纹萌生区。
Cyclic deformation characteristics and the distribution of deformation twins in a recently developed magnesium alloy AM30 after strain-controlled low cycle fatigue tests were studied in the loading direction along the extrusion direction. The alloy was basically cyclically stable at a lower strain amplitude of 0.2% with low stress amplitude and small plastic strain amplitude, while it exhibited strong cyclic hardening at a higher strain amplitude of 0.6%. In addition to the initially high stress amplitude and large plastic strain amplitude, the stress amplitude increased and plastic strain amplitude decreased significantly as cyclic deformation proceeded at the higher strain amplitude. Twinning in compression and detwinning in tension occurred at both strain amplitudes, and the distribution of the residual twins observed near the fracture surface was a consequence of competition between twinning and detwinning, depending on the strain amplitude, cyclic hardening–softening characteristics, and the plastic zone size ahead of the crack tip. In the stable cyclic deformation at the lower strain amplitude, deformation twins appeared mostly in the area prior to the final rapid fracture, while at the higher strain amplitude with cyclic hardening the extensive and well-developed twins were mainly observed in the crack initiation area.