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Microstructural evolution and micromechanical modelling of the mechanical behavior of a ceramic particle-reinforced metal matrix composite.

机译：陶瓷颗粒增强金属基复合材料力学行为的微观结构演变和微观力学建模。

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摘要

The objective of this study was to develop a thorough understanding of the precipitation characteristics and mechanical behavior of a 2124 Aluminum alloy reinforced with 13.2 volume% SiC whiskers. Microstructural development of the 2124 Al-SiC composite subject to controlled and systematic aging treatments was investigated using various techniques. The results indicate that the matrix of the composite material has a much greater dislocation density than the control alloy. The increased dislocation density facilitates the nucleation of the strengthening precipitates whereby the incubation time for precipitate nucleation and the time to reach peak hardness in the matrix of the composite are significantly reduced. Theoretical analysis of dislocation generation due to thermal contraction mismatch and of the punching of dislocations at whisker ends are examined in the context of microstructural development.; An experimental and theoretical investigation into the uniaxial stress-strain response of the 2124 Al-SiC whisker composite system was undertaken where the effects of accelerated aging of the matrix of the composite were incorporated into the modelling of deformation behavior. The 0.2% offset yield strength was found to be independent of aging state, whereas the strain to failure was found to decrease monotonically with an increase in aging time for the composite. A self-consistent approximation was formulated and was found to provide the most accurate predictions for the elastic response of the composite. A finite-element unit-cell model was used to predict the plastic response of the composite material.; The effects of SiC reinforcement and matrix aging treatment on crack growth under quasi-static and fatigue loading were also investigated. The composite exhibits a fatigue threshold value which is about twice that of the control alloy. However, the fatigue threshold is relatively insensitive to variations in both the aging treatment and the mean stress of the fatigue cycle in both the composite and control alloy. The resistance to quasi-static crack growth of the composite is reduced with increases in aging time with the overaged microstructure exhibiting perfectly brittle behavior.
机译：这项研究的目的是深入了解23.2体积％SiC晶须增强的2124铝合金的析出特性和力学性能。使用各种技术研究了2124 Al-SiC复合材料在受控和系统的时效处理下的微结构发展。结果表明，复合材料的基体具有比对照合金大的位错密度。位错密度的增加促进了强化析出物的形核，从而显着减少了析出物形核的保温时间和达到复合材料基体硬度峰值的时间。在微结构发展的背景下，对由于热收缩失配而产生的位错和晶须端部的位错冲孔的理论分析进行了研究。对2124 Al-SiC晶须复合材料系统的单轴应力-应变响应进行了实验和理论研究，其中将复合材料基质加速老化的影响纳入了变形行为的建模中。发现0.2％的偏移屈服强度与时效状态无关，而发现破坏应变随着复合物时效时间的增加而单调降低。制定了自洽近似，发现可以为复合材料的弹性响应提供最准确的预测。有限元晶胞模型用于预测复合材料的塑性响应。还研究了SiC增强和基体时效处理对准静态和疲劳载荷下裂纹扩展的影响。该复合材料的疲劳阈值约为对照合金的疲劳阈值的两倍。但是，疲劳阈值对复合合金和对照合金中的时效处理和疲劳循环平均应力的变化相对不敏感。随着老化时间的增加，复合材料对准静态裂纹扩展的抵抗力降低，而过时效的显微组织表现出完美的脆性。

著录项

  • 作者

    Christman, Thomas Aurele.;

  • 作者单位

    Brown University.;

  • 授予单位 Brown University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 1989
  • 页码 144 p.
  • 总页数 144
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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