Modelling of hardening due to grain growth for a superplastic alloy

Combined analytical and numerical optimisation procedures have been developed to determine the material constants in superplastic constitutive equations. The conventional grain growth rate equation has been modified to enable accurate modelling of the isothermal and plastic-strain-induced grain growths for different microstructures of a titanium alloy. A set of unified viscoplastic constitutive equations for Ti–6Al–4V at 927°C, which incorporates isotropic hardening and grain growth, has been fully determined from experimental data for different initial grain sizes and strain rates. Close agreement between the predicted and experimental stress–strain relationships has been achieved. In addition, the contributions of hardening constituents, such as strain-rate hardening, isotropic hardening and the hardening due to grain growth have been modelled.