Effect of electrochemical hydrogen charging on the mechanical behavior of a dual-phase Ti–4Al–2V–1Mo–1Fe (in wt.%) alloy

Abstract The effect of electrochemical hydrogen charging on the mechanical properties and fracture behavior of a dual-phase Ti–4Al–2V–1Mo–1Fe (Ti4211) alloy was investigated. It revealed that after being electrochemical charged at a constant cathodic current density value of 100 mA/cm2 for 4 h, 8 h and 24 h, needle-like δ-TiHx hydrides were formed in the interior of α-Ti phases and at α-Ti/β-Ti interfaces. For the sample being charged for 4 h, α-Ti phases near the hydrogen charging direction could be completely transformed into hydrides and formed a hydride layer with an average thickness of 160 μm. As for the samples being charged for 8 h and 24 h, the thicknesses of the hydride layers were respectively increased to 230 μm and 380 μm. Tensile results demonstrated that with the charging time being increased from 0 h to 24 h, the elongation ratio to failure (ef) was decreased from 13.2% to 0.6%. The reason for ductile degradation was attributed to the stress concentration effect caused by the preferential cracking of hydride layers.