Physical constitutive modelling of hot deformation of titanium matrix composites

Second-phase particles have complex effects on the micro- and macro-deformation behaviours of titanium matrix composites (TMCs). Therefore, it is difficult to accurately predict the microstructure evolution and flow stress during their hot working. To address this issue, this paper presents a physical unified constitutive model for TMCs. In the model, the dislocation evolution is modelled by considering the geometrically necessary dislocations introduced by the mismatches of the elastic modulus and thermal expansion coefficient between the second-phase particles and matrix material, and the dynamic recrystallization (DRX) is modelled by considering the role of second-phase particles in promoting DRX grain nucleation and inhibiting DRX grain growth. Subsequently, the constitutive equation is developed considering the contributions of thermal activation stress, hardening by dislocation multiplication, DRX softening, second-phase particles dispersion strengthening, and Hall–Petch strengthening. The developed unified constitutive model is used to quantitatively investigate the effects of second-phase particles on the flow behaviour and microstructure evolution during the hot working of the (TiC+TiB)/Ti–6Al–4V alloy. This study is of great significance for optimising the hot-working parameters of TMCs.