Ti-Ni形状記憶合金のマルテンサイト相変形に及ぼす水素の影響

抄録

Effect of a small amount of hydrogen on the deformation of martensite phase in a Ti-50.0 at. %Ni shape memory alloy was investigated. Mechanical properties such as tensile strength, total elongation and reduction of area decreased even with a small amount of hydrogen. On the one hand, the stress for the self-accommodation process of martensite variants and the elongation corresponding to this process were not influenced by hydrogen. These results indicated that the influence of hydrogen on mechanical properties arose in the later stage of deformation where slip deformation was introduced. In the case of cyclic deformation, cyclic stress decreased because of interaction between hydrogen and dislocations which were introduced during deformation cycles. From the results of hydrogen discharge tests and low electric current density of cathodic charging, hydrogen which interacts with dislolations is considered to be in solid sulution state. Hydrogen which is released from the trap sites of a weak binding energy can also be taken into consideration.