| Co-Investigator(Kenkyū-buntansha) |
KURISHITA Hiroaki Graduate School of Engineering Sciences, Kyushu University, 総合理工学研究科, 助手 (50112298)
KUWANO Noriyuki 九州大学, 総合理工学研究科, 助教授 (50038022)
TOMOKIYO Yoshitsugu Faculty of Engineering, Kyushu University, 工学部, 助教授 (40037891)
GOTO Shoji Graduate School of Engineering Sciences, Kyushu University, 総合理工学研究科, 助教授 (50005948)
OKI Kensuke 九州大学, 総合理工学研究科, 教授 (70037860)
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| Research Abstract |
The relation between the interface structure and strength in metals, ceramics and their composites has been investigated. The results are summarized as follows.
1. Extended Grain-Boundary: From the prepared bicrystals of Mo, Si and SiC, it is found that the width of grain boundaries is very narrow in Mo and Si and the grain-boundary strength depends on the misorientation at the boundary, whereas the width is as wide as several nano meters in SiC and the strength is almost independent of the misorientation. Such a wide boundary is also observed in other several non-oxide ceramics. From these findings a theory of extended boundary is proposed for the materials with polarity.
2. Composite Materials: By using Ni-SiO_2, Al-Be, Al-Al_6Mn, Al-Mg-Be and Al-Mg-Al_6Mn, each of which is a characteristic dispersion hardened alloy, the shape-effect of dispersed particles on the high-temperature strength and the interaction of dislocations with particles have been investigated. It is found that the shape effect is strong in Ni-SiO_2, and in the Al alloys the interaction is attractive and the strengthening effect of this interaction is equivalent to that of void hardening. This concept of hardening is applicable to other dispersion-hardended alloys. This kind of interaction is favorable for the high-temperature strength of dispersion-hardened alloys, but it is unfavorable for that of lamellar composites. This idea is verified by using Mo-TiC lamellar composite. The effects of lamellar width and colony size on the strength are also shown for Al-CuAl_2 alloys.
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