| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
Mesoscopic structure controlling for supercomposites (in-situ composites reinforced with refractory metal fibers) was carried out by solidification speed change, the 4th-element addition and heat treatment. Consequently, we found that as the solidification rate increase, the inter-phase distance of reinforcements decreases, the diameter of the cell formed in the inside of a sample increase, and the shape of alpha phase changes from fiber-like shape to lamella-like one. Furthermore, as a result of adding Re and Ir as the 4th element, we found that inter-phase distance became large and its morphology also changed to lamella by addition of both elements. The structural stability of supercomposite sample was investigated at elevated temperature, and there was no interface reaction phase between fiber and matrix. The heat treatment of a maximum of 500 hours was performed and hardness change and morphology change of supercomposite were investigated. It was shown clearly that the hardness of additive-free samples decreased about 10% by heat treatment of 500 hours, the decrease in hardness of the sample, which added Re, and Ir as the 4th element was small and that these two elements raised the high temperature stability of supercomposite. The high temperature tensile test for the structural controlled supercomposite was performed, and high temperature strength and high temperature ductility were evaluated. Consequently, the samples showed the ultimate tensile strength of a maximum of 1198 MPa at 800℃, and this high temperature strength was equivalent to that of commercial nickel-base superalloys, such as Mar-M247 and CMSX-2. As a result of the high temperature oxidization test, supercomposite had the oxidation resistance superior to the commercial nickel-base superalloy, and it was shown that the oxidation resistance was further improved by adding of Re and Ir.
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