Effect of hydride and hydrogen-induced martensite on fracture toughness of TiNi alloy

The hydride formed in hydrogen charging TiNi shape memory alloy could decrease evidently fracture toughness K-IC of the TiNi alloy and the relative loss of KIC is as high as 96%. The relative loss of KIC induced by the hydrogen induced martensite, however, is only about 1.8%, and does not change evidently with hydrogen concentration. Therefore, the decrease in fracture toughness of hydrogenated specimen is almost completely attributed to hydride. The relative loss of KIC induced by hydrides, DeltaK(IC)(TiNiH)/K-IC, increases with increasing hydride content WriNffl, i.e, DeltaK(IC)(TiNiH)/K-IC(%)=93 [GRAPHICS] . Microcracks could be generated along the hydrides during charging at i greater than or equal to 15 mA/cm(2) 9.5 and do not cause farther the decrease in K-IC.