Enhanced gradient crystal-plasticity study of size effects in a β-titanium alloy

A calibrated model of enhanced strain-gradient crystal plasticity is proposed, which is shown to characterize adequately deformation behaviour of b.c.c. single crystals of a β-Ti alloy (Ti-15-3-3-3). In this model, in addition to strain gradients evolving in the course of deformation, incipient strain gradients, related to a component's surface-to-volume ratio, is accounted for. Predictive capabilities of the model in characterizing a size effect in an initial yield and a work-hardening rate in small-scale components is demonstrated. The characteristic length-scale, i.e. the component's dimensions below which the size effect is observed, was found to depend on densities of polar and statistical dislocations and interaction between them.