Stress corrosion cracking of the titanium alloys under hydrostatic pressure resulting from the degradation of passive films

Stress corrosion cracking of Ti-6Al-4 V under hydrostatic pressure was studied based on experimental characterization and first-principles calculation. As a consequence of the water pressure, the passive films equipped with tensile stress become unstable, which might result from the dissolution of vanadium. The work function confirms that vanadium is environmentally sensitive and becomes surprisingly active under hydrostatic pressure. This selective dissolution provides an acid circumstance, although in the neutral 3.5% NaCl solution. Meanwhile, hydrostatic pressure also affects the adsorption and penetration of hydrogen, thus promoting the stress corrosion of titanium alloy. With the pressure, hydrogen ingresses into titanium and then incubates cracks by accelerating dislocation motion. Our efforts provided a basis for designing titanium alloys with higher tolerance to pressure changes, by selecting a class of alloying elements with little change in chemical stability even in extreme environments.