Stress-corrosion Cracking Susceptibility of Tungsten-inert-gas-welded TC4 Titanium Alloy Joints under Low Strain Rates

The microstructure of tungsten-inert-gas (TIG)-welded TC4 titanium alloy joints was analyzed. The stress-corrosion behavior and hydrogen embrittlement susceptibility of the welded joints were also studied by performing slow strain rate tensile tests (SSRTs) in 3.5% NaCl solution. The results show that the heat-affected zone was mainly composed of alpha, beta, and alpha' phases, in which the alpha' phase comprised a coarse-grain region with a reticulated morphology. During tensile tests, the stress-corrosion sensitivity of the welded joints increased with increasing strain. The greatest stress-corrosion sensitivity occurred at a strain rate of 0.24 mm/min, where the joint fractured at the fusion line. Regarding the hydrogen embrittlement sensitivity, the fracture strength of the joints increased and the elongation percentage decreased with increasing polarization potential. In addition, the fracture surface was primarily composed of dimples, showing that the joints were not sensitive to hydrogen embrittlement.