| Co-Investigator(Kenkyū-buntansha) |
MITOSE Kengo Furukawa Electric Co.Ltd., Yokohama R & D Laboratory, Researcher, 横浜研究所, 研究員
SUZUKI Yuichi Furukawa Electric Co.Ltd., Yokohama R & D Laboratory, Director, 横浜研究所, 所長
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| Research Abstract |
To improve the shape memory characteristics of Ti_<50>Pd_<50-x>Ni_x (0<=x<=50) high temperature shape memory alloys, various experiments were carried out, and the following results were obtained. (1) A new apparatus to assess high temperature shape memory characteristics was developed, utilizing differential transformers to avoid the effect of thermal expansion of various parts of the system. Although some troubles were encountered at the beginning, the troubles were eliminated by using quartz glass rods with very low thermal expansion to detect the strains of specimens. (2) The addition of B to the above alloys were found to be effective to prohibit grain growth, and to the resultant increase of elongation of the alloys. The expected precipitates of TiB_2 were also realized, but the size was too large to be effective. The large grain growth of TiB_2 precipitates were found to originate in the homogenization annealing prosess. Thus, the homogenization treatment was avoided thereafter.
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(3) Since the precipitation hardening of TiB_2 was not effective, another type of precipitation hardening was tried. i.e.the composition of Ti was changed from the stoichiometry of Ti_<50>Pd_<30>Ni_<20>. As a result, the method was found to be effective with introduction of another precipitates. (4) Starting from Ti_<50>Pd_<30>Ni_<20> alloys, 4 types of alloys with B addition, Ti-rich from stoichiometry, and the combination of both, were prepared. Then, as a result of optimization experiment with respect to composition and heat-treatment, the high temperature shape memory characteristics were found to be best for the alloy on Ti-rich side, which were heat-treated at 773K for 1h. (5) Very interesting results were obtained on the recovery・recrystallization of the alloys. i.e. The recovery・recrystallization was found to be controlled by the reverse transformation such that the former follows the latter. (6) Very interesting phenomenon was found such that recrystallization occurs in the martensitic state. However, this means that the recrystallization in the martensitic state becomes one factor determining the upper temperature limit of the alloys. (7) Cyclic experiments are being done using the above new apparatus. However, the cyclic experiments are to be continued in the following year, since the experiments are very time-consuming (i.e.10h/specimen). Less
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