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Plastic deformation and work hardening of aluminum and AA5754 aluminum alloys.

机译：铝和AA5754铝合金的塑性变形和加工硬化。

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摘要

This research has been carried out to understand the relation between work hardening, deformation behaviour, dislocation substructure and crystallographic texture developed during plastic flow in pure Al and continuous cast and direct chill cast AA5754 Al-Mg alloys. Tensile and strain rate sensitivity tests are performed in the temperature range 4.2K-295K details of the process of dislocation accumulation, the dislocation substructure development and texture evolution are followed using a range of techniques such as TEM, in-situ resistivity measurements and X-ray diffraction. The tensile deformation results show an unprecedented level of strength and unusual work hardening behaviour of Al-alloys at 4.2K. The electrical resistivity data suggest that fracture is initiated by the collapse of the dislocation network at places where dislocations develop a critical spacing for spontaneous annihilation. This spacing is estimated at approximately 8nm at 4.2K for both pure Al and Al alloys and &sim12nm at 78K for pure Al. Strain rate sensitivity measurements suggest that deformation of high purity Al is governed by dislocation-dislocation interactions in a broad range of temperatures, whereas Al alloys exhibit a larger thermal component of flow stress due to the presence of solute atoms in the matrix. The texture studies show that, independently of initial texture, the tensile axis of deformed samples rotates to (111) stable end orientation, and the intensity of the (111) peak increases parabolically with the flow stress, also strongly affected by the temperature. The experiments carried out on samples oriented at different angles to the rolling direction indicate that the crystallographic texture is the major factor responsible for the anisotropy of the alloys mechanical properties. This is attributed to the effect of the operating slip systems activated during tensile deformation. The Visco-Plastic Self Consistent modeling has been carried out to predict mechanical behaviours of AA5754 alloys and to provide insight into operating mechanisms of plastic flow as well as the origin of the anisotropy of mechanical properties. These results indicate that the more effective dislocation storage in the substructure at a low temperature significantly increases the work hardening rate at the later stage of deformation, and the crystallographic texture is the major cause of the anisotropy in the flow stress behaviour.
机译：进行这项研究是为了了解纯Al以及连续铸造和直接冷铸AA5754 Al-Mg合金在塑性流动过程中产生的加工硬化，变形行为，位错亚结构和晶体织构之间的关系。在位错积累过程的详细信息4.2K-295K的温度范围内进行了拉伸和应变率敏感性测试，使用了一系列技术（例如TEM，原位电阻率测量和X-射线衍射。拉伸变形结果表明，在4.2K时，铝合金具有前所未有的强度和异常的加工硬化行为。电阻率数据表明，断裂是由位错网络在位错形成自发an灭的临界间距的位置坍塌而引发的。对于纯Al和铝合金，此间距在4.2K时约为8nm，对于纯Al在78K时约为sim12nm。应变速率敏感性测量表明，高纯度Al的变形受温度范围内位错-位错相互作用的影响，而铝合金由于基体中存在溶质原子而表现出较大的流动应力热分量。纹理研究表明，与初始纹理无关，变形样品的拉伸轴旋转到（111）稳定的端部取向，并且（111）峰的强度随流动应力呈抛物线形式增加，并且也受到温度的强烈影响。在与轧制方向成不同角度取向的样品上进行的实验表明，晶体织构是造成合金力学性能各向异性的主要因素。这归因于在拉伸变形期间激活的工作滑动系统的作用。进行了粘塑性自洽模型来预测AA5754合金的力学行为，并提供对塑性流动的运行机理以及力学性能各向异性起源的深入了解。这些结果表明，在低温下更有效的位错存储在子结构中会显着提高变形后期的加工硬化速率，并且晶体织构是流动应力行为各向异性的主要原因。

著录项

  • 作者

    Park, Dong-Yeob.;

  • 作者单位

    McMaster University (Canada).;

  • 授予单位 McMaster University (Canada).;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 240 p.
  • 总页数 240
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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