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A study on crystal plasticity of face-centered cubic structures induced by deformation twinning
Acta Materialia ( IF 9.4 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.actamat.2020.07.040
M.S. Szczerba , S. Kopacz , M.J. Szczerba

Abstract The effect of deformation twinning on the accessible slip and twin shear systems of a dislocated face-centered cubic structure and their critical stresses is studied. In particular, the plastic shear modes of critical matrix structure – single glide oriented Cu-8at.%Al alloy crystals deformed by room temperature tension up to the onset of deformation twinning - and the plastic shear modes of bimodal twin/matrix layered structure – subsequently twinned Cu-8at.%Al crystals – were examined. It was found that all twin and slip systems of the matrix structure may operate independently and their critical stresses are dispersed by about fifteen percent around the mean value. However, not all of the accessible slip and twin systems of the twin/matrix structure may operate independently and their critical stresses may differ by a factor of well over four. This large discrepancy of the critical stresses is responsible for giant yield stress anisotropy of the twin/matrix layered structure; the maximal and minimal yield stresses may differ even by one order of a magnitude. The twin/matrix layered structure reveals also very strong asymmetry of the tension/compression yield stress. It is suggested, that the giant anisotropy and very strong asymmetry of the yield stress have the same physical origin, i.e. the internal stress field associated with extended configurations of cube dislocations located within a twin lamellae - the deformation twinning induced effect of cube dislocation stress. It is concluded, that the cube dislocation stress effect seems greatly responsible for plasticity and strengthening of mechanically twinned face-centered cubic structures.

中文翻译:

变形孪晶诱导的面心立方结构晶体塑性研究

摘要 研究了变形孪生对位错面心立方结构的可及滑移和双剪切系统及其临界应力的影响。特别是,临界基体结构的塑性剪切模式——单次滑动取向的 Cu-8at.%Al 合金晶体在室温张力下变形直至变形孪晶开始——以及双峰孪晶/基体层状结构的塑性剪切模式——随后检查了孪晶 Cu-8at.%Al 晶体。发现基体结构的所有孪生和滑移系统都可以独立运行,它们的临界应力分散在平均值附近约 15%。然而,并非双/矩阵结构的所有可接近的滑动和双系统都可以独立运行,它们的临界应力可能相差四倍以上。临界应力的这种巨大差异是造成双/矩阵层状结构巨大屈服应力各向异性的原因;最大和最小屈服应力甚至可能相差一个数量级。双/基体层状结构也显示出非常强的拉伸/压缩屈服应力不对称。这表明,屈服应力的巨大各向异性和非常强的不对称性具有相同的物理起源,即与位于孪晶层内的立方位错的扩展构型相关的内应力场——立方位错应力的变形孪晶诱导效应。结论是,
更新日期:2020-09-01
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