Effect of hydrogen on superplastic deformation of (TiB + TiC)/Ti–6Al–4V composite

Ti–6Al–4V matrix composite reinforced with TiB plus TiC was prepared and hydrogenated. The phases were identified by X-ray diffraction (XRD). Microstructures were examined by optical microscopy (OM). Dependence of transus temperatures of the composite on hydrogen concentration was determined. The result shows hydrogen decreases transus temperatures of the composite significantly and increases the amount of β phase. Superplastic deformation of the hydrogenated composites was performed. Hydrogen decreases the optimum superplastic temperatures and increases the optimum superplastic strain rate. The flow stresses of hydrogenated composites decrease greatly compared to unhydrogenated composite. The strain rate sensitivity index m of the composite increases with increasing hydrogen concentration and reaches maximum 0.327 at 0.85 wt.% H. Meanwhile, the activation energy Q decreases with increasing hydrogen concentration and ranges in 488–382 kJ/mol. Hydrogen promotes recrystallization of the composite and refines the microstructure during superplastic deformation.