日本金属学会誌

J. Japan Inst. Metals, Vol. 48, No. 2 (1984),
pp. 115-121

Degradation and Improvement of Shape Memory Effect of Cu-Base Alloys

Kenichi Murakami1, Yukihisa Murakami2, Kenji Mishima3 and Yasushi Ikai4

1Graduate Student, Kobe University, Kobe
2Faculty of Engineering, Kobe University, Kobe. Present address: Ezaki Glico. Co., Ltd., Osaka
3Graduate Student, Kobe University, Kobe. Present address: Himeji Institute of Technology, Himeji
4Faculty of Engineering, Kobe University, Kobe

Abstract:

Resistivity to degradation due to repeated martensitic transformation of Cu-base shape memory alloys is evaluated through optical reflectivity measurements. The repeated martensitic transformation generates dislocations and then internal stress. Irreversible martensites become to appear, and they accommodate them selves to the internal stress. They are increased in amount with increasing thermal cycles. Internal stress shifts Ms to a higher temperature side and Mf to a little lower temperature side.
Cu-Zn-Al alloys with finer grain size are more resistive to thermal cycling. One of them with the finest grain size has nearly the same thermal resistivity as a Ti-Ni allay. The grain size refinement is done by adding small quantities of Ni, Pb, Ce, Cr, B, and Zr. The Cu-Zn-Al allay with the smallest grain size (≤20 μm) shows less sharp hysteresis curves.


(Received 1983/05/20)

Keywords:

shape memory effect, copper-base alloys, cyclic thermal loading, irreversible martensites, dislocation multiplication, internal stress, grain size refinement, reflectivity


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