日本金属学会誌

J. Japan Inst. Metals, Vol. 50, No. 1 (1986),
pp. 1-10

Effect of the Heat Treatment after Cold Working on the Phase Transformations in Ti-Ni Alloys

Tsunehiko Todoroki1 and Hirokazu Tamura2

1Air-conditioner Division, Matsushita Electric Industrial Co., Ltd., Kusatsu
2Central Research Lab., Furukawa Electric Co., Ltd., Tokyo

Abstract:

Three types of phases, the CsCl(B2) type, the rhombohedral (R) type and the monoclinic (M) type, are recognized in near-equiatomic Ti-Ni alloys. The effect of the heat treatment (633 K--933 K) after cold work on the phase transformations among these three phases in three Ti-Ni alloys (49.7, 50.2 and 50.6 at%Ni) has been investigated by D.S.C. measurement.
The results are summarized as follows:
(1)  The phase transformations are classified into the following three types according to the heat treatment temperature; (a) B2→R→M during cooling and M→R→B2 during heating for lower heat treatment temperatures; (b) B2→R→M during cooling and M→B2 during heating for intermediate heat treatment temperatures; and (c) B2→M during cooling and M→B2 during heating for higher heat treatment temperatures.
(2)  The more the Ni content increases, the larger the temperature range for the R-phase to exist becomes and the more the R-phase transformation temperature decreases with the increase of the heat treatment temperature. But the R-phase transformation of the alloys heat-treated at 633 K starts at about 330 K, which is almost independent of the Ni content.


(Received 1985/6/28)

Keywords:

titanium-nickel alloy, shape-memory alloy, heat treatment, annealing, phase transformation, martensitic transformation, differential scanning calorimetry, electrical resistance


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