日本金属学会誌

J. Japan Inst. Metals, Vol. 56, No. 7 (1992),
pp. 747-756

Effect of Hydrogen on Transformation Characteristics and Deformation Behavior in a TiNi Shape Memory Alloy

Taiji Hoshiya1, Shoji Den2, Hiroshi Katsuta3 and Hiroei Ando1

1Oarai Research Establishment, Japan Atomic Energy Research Institute, Oarai, Ibaraki
2Development and Research Laboratory, IRIE KOKEN Co., LTD., Kawagoe
3Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki

Abstract:

Transformation characteristics and deformation behavior of hydrogenated Ti-50.5 at%Ni alloys, which were occluded in a low pressure range of hydrogen between 1.1 and 78.5 kPa, have been studied by electrical resistivity measurement, tensile test, X-ray diffraction analysis and microstructural observation.
Ms temperature of the Ti-Ni alloys decreased with an increase in hydrogen content. This corresponds to the stabilization of the parent phase during cooling, which was confirmed by X-ray diffraction: The suppression effect of hydrogen takes place on the martensitic transformation.
Critical stress for slip deformation of hydrogenated Ti-Ni alloys changed with hydrogen content and thus hydrogen had a major influence on deformation behavior of those alloys. With hydrogen contents above 0.032 mol%, hardening was distinguished from softening which was pronounced in the contents from 0 to 0.032 mol%H.
Hydrides were formed in hydrogen contents over 1.9 mol%. The hydride formation results in the reorientation in variants of the R phase and an increase in the lattice strains of the parent phase.


(Received 1991/08/28)

Keywords:

shape memory effect, titanium-nickel alloy, martensitic transformation, electrical resistivity, hydrogen, deformation behavior, elastic energy


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