| Research Abstract |
The metal matrix composites were fabricated by the squeeze casting, semi-solid casting, stirring casting and the hot pressing. Reinforcements used in this study are mainly SiC, AlィイD218ィエD2BィイD24ィエD2OィイD233ィエD2, TiOィイD22ィエD2 particles/whisker/fiber and matrices are aluminum, magnesium and titanium alloys. Furthermore, Niobium/MoSiィイD22ィエD2 lamellar composites were fabricated by hot pressing. At first, the relationship between the fabrication condition and the mechanical properties were investigated. Then, in order to investigate the control factor of the mechanical properties, the microstructure, the deformation and the fracture structure were observed in atomic scale by the scanning and transmission electron microscopy. The main control factors are the deterioration of the reinforcement, the structure changes of the ceramics/matrix interface and the change of the matrix microstructure (or character). We focused the investigation of the effect of interface structure and reaction on the deformation and fracture. By considering the control method of the interface structure, we presented the design principle of the composite fabrication.
Following is the topics in this study. Interface reaction temperature of TiOィイD22ィエD2/Al composite decreased by the doping the third element for the surface of the TiOィイD22ィエD2 particles. Heat stability of the AlィイD218ィエD2BィイD24ィエD2OィイD233ィエD2 whisker / Al, Mg alloy matrix composites increased by the formation of the thin and homogeneous MgAlィイD22ィエD2OィイD24ィエD2 layer on the whisker. Nb/MoSiィイD22ィエD2 lamellar composites having high fracture toughness was fabricated by the addition of the third elements to MoSiィイD22ィエD2 sheet. In fiber-reinforced composites, it is found that the creep rupture lifetime was predicted by the probability model considering the time dependence of the load resistance of the fiber.
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