Dependence of K_ISCC on Loading Rate and Crack Orientation in Ti-6Al-6V-2Sn^⋆

The dependence of K_ISCC on loading rate was investigated for Ti-6Al-6V-2Sn in 3.5% NaCl for both the WR and RW orientations. Crack initiation was determined to occur when a spike in electrochemical potential was observed. The measured K_ISCC values were a minimum at an intermediate loading rate, which is indicative of hydrogen embrittlement through hydride formation. The strain rate at which minimum K_ISCC values were observed corresponded closely with the theoretical minimum strain rate for hydrogen transport by dislocations as Cottrell atmospheres. K_ISCC values were lower for RW specimens than for WR specimens due to a more favorable orientation of hydride habit planes with respect to the tensile axis.