The effect of hydride and martensite on the fracture toughness of TiNi shape memory alloy

摘要

The effect of hydride and hydrogen-induced martensite on the fracture toughness of a TiNi shape memory alloy has been investigated using a notched tensile specimen. The results show that the fracture toughness of the hydrogenated samples decreases linearly with increasing hydrogen concentration, and the relative fracture toughness loss is as high as 96%. The relative fracture toughness loss induced by the martensite, however, is about 1.8%, and is independent of hydrogen concentration. The decrease in the fracture toughness of hydrogenated samples is almost completely due to the hydride. The relative fracture toughness loss induced by the hydride, DeltaK(IC)(TiNiH)/K-IC, increases with increasing hydride content, W-TiNiH, i.e., DeltaK(IC)(TiNiH)/K-IC (%) = 93[1-exp(-W-TiNiH/9.5)]. Microcracks can generate along the hydrides during charging at i greater than or equal to 15 mA cm(-2), but do not further increase the relative fracture toughness loss induced by the hydride.