Analysis and control of microstructure of metal matrix composite under stress loading

本研究旨在分析颗粒增强金属基复合材料在静态加载过程中颗粒、基体及其界面的微观行为，明确其制备工艺对其行为的影响。本文首先研究了在扫描电子显微镜上进行的原位拉伸试验。结果，成功地检查了测试，并且可以观察到由于均匀应力分布下的结构缺陷而导致的仅微观结构退化。用粉末挤压法和熔体搅拌法制备了Al_2O_3和SiC颗粒弥散铝合金复合材料。通过原位拉伸试验，连续观察了复合材料在拉伸过程中微观结构的变化。在最大载荷之前的早期加载点，由于界面脱粘和颗粒断裂，所有复合材料中的一些微裂纹开始。由于基体的韧性，微裂纹不会在基体中扩展，但随着应变的增加，新裂纹的数量增加。微裂纹的性质及其变化与复合材料的制备工艺有关。

The present research aims at analyzing microscopic behavior of particles, matrix and their interfaces of particle reinforced metal matrix composites during static loading and making clear the effects of their fabricating processes on the behavior. The in situ tensile test in the scanning electron microscope equipped with a defromation stage was investigated at the first of all. As the result the test was successfully examined and it was possible to observe only microstructural degradation owing to structural defects under homogeneous stress distribution. It was also found that the same microstructural degradation was occurred inside the specimen as wel as that observed on its surface.Some Al_2O_3 and SiC particle dispersed aluminum alloy composites were produced with the powder extruding and melt stirring methods. The change in microstructure of the composites was observed continuously during tensile loading by the in situ tensile test. Some microcracks owing to the interface debonding and the particle fracture are initiated at early loading point before maximum loading in all composites. The microcracks do not propagate in the matrix because of its ductility, but the number of new microcracks are increased with inceasing strain. The character of the microcracks and their change are depend on the fabricating process of the composites.