Stress Corrosion Cracking Behavior of TC4 Titanium Alloy in 3.5%NaCl Solution
A stress corrosion cracking(SCC)test of TC4 titanium alloy in 3.5%NaCl solution was carried out,using wedge opening loading(WOL)specimens.The SCC behavior and mechanism were analyzed.The results show that the SCC propagation can be identified on the surface of specimen after 24 hours.The SCC lengths of specimens corroded for 30 days are similar with that of the specimens corroded for 75 days.And both are significantly longer than that of the specimens corroded for 15 days.This indicates that SCC propagation terminated within 15-30 days.The SCC crack length increases with the enhancement of loading stress.Stress relaxation occurs along with crack extending,resulting in continuous reduction of residual KI.When residual KI value decreases to about 38 MPa·m1/2,SCC propagation terminates.SCC behavior of the specimen could be attributed to coupling effect of stress and corrosion.Stress dominates the fast crack propagation at the initial stage of SCC,and the fracture surface presents dimple morphology.While the fracture surface exhibits cleavage morphology with scaly pattern at middle and later stages of SCC.And titanium oxide is found at the edge of scaly pattern.That is supposed to result from alternate repetition of crack residency after stress relaxation and crack continuous propagation assisted by anodic dissolution
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