| सारांश: | The metastable β titanium alloys used in marine engineering applications suffered from stress-corrosion cracking in seawater. The different phase composition leads to the distinct stress-corrosion cracking behaviors of the alloy. In this work, the influence of the phase composition on the stress-corrosion cracking of a novel metastable β titanium alloy Ti-6Mo-5V-3Al-2Fe-2Zr was investigated. The alloys with different phase compositions were prepared by three types of thermal-mechanical processing, i.e., the single β phase (assigned as M<sub>(β)</sub>), the β phase plus fine α phase (assigned as M<sub>(β+fα)</sub>), and the β phase plus coarsened α phase (assigned as M<sub>(β+cα)</sub>). The electrochemical tests and constant-stress loading tests were performed, and the phase composition and microstructure were analyzed by XRD and SEM. The M<sub>(β)</sub> alloy exhibits the best corrosion resistance as well as the compact properties of oxide films, followed by the M<sub>(β+fα)</sub> alloy and the M<sub>(β+cα)</sub> alloy. Tear ridges and a flat facet with an undulating surface were observed on the stress-corrosion cracking fracture surface, which indicated the occurrence of high-degree dislocations movement and localized plastic deformation. Absorption-induced dislocation emission (AIDE) and hydrogen-enhanced localized plasticity (HELP) are the primary mechanisms for the stress-corrosion cracking of the alloy. The increased amount of β phase has a beneficial effect on stress-corrosion cracking resistance. For the alloy with β and α phases, the α phase with wider spacing has an adverse effect on stress corrosion performance.
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