Kazuhiro Matsugi, Yong-Bum Choi and Gen Sasaki
Graduate School of Engineering, Hiroshima University, Higashihiroshima 739-8527
Optimization in both alloy-composition and manufacture-process has been required to obtain the TiNi-X compounds with high-strength and -oxidation resistance. Both Ti-49 mol%Ni-1 mol%Cr and Ti-45Ni-5Cr were designed for the achievement of tensile strength of 500 MPa and 800 MPa, respectively, and high oxidation resistance, by the d-electrons concept. The levitation melted castings showed the limited contamination amount and homogeneous microstructure. The values of tensile strength for Ti-49Ni-1Cr and Ti-45Ni-5Cr castings without solidification defects were 585 MPa and 840 MPa, which meant the achievement of the target values. The oxidation amount of Ti-45Al-5Cr was 0.28 times, compared with Ti-50Ni. It is concluded that TiNi-X intermetallic compounds having the objective constructed phase, tensile strength and oxidation resistance, are obtained successfully by the theoretical alloy design, without doing any trial-and-error experiments.
sharp memory alloys, oxidation resistance, solidification defects, levitation melting, alloy design
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