Effects of basal-pyramidal dislocation lock on intergranular deformation incompatibility in near-α titanium alloy

This work investigates the configurational evolution of basal-pyramidal (B-P) dislocation locks in TA18 alloy and their influence on deformation incompatibility. We reveal that complex dislocation reactions lead to significant intergranular deformation heterogeneity, even under conditions of low slip transmission resistance. Specifically, basal 〈a〉 dislocations interact with pyramidal 〈c + a〉 dislocations to form sessile B-P locks, which significantly impede dislocation motion and induce localized stress concentrations. Furthermore, we characterize the metastable nature of pyramidal 〈c + a〉 dislocation within the B-P lock and elucidate its dissociation into basal 〈a〉 and prismatic 〈c〉 dislocations. This dissociation is identified as a thermodynamically driven process of dislocation core reconstruction, ultimately facilitating plastic flow. The physical origin of dislocation dissociation lies in the transformation of high-energy dislocation cores into low-energy configurations on alternative slip planes. These findings provide valuable insights into the multi-scale coupled mechanisms governing plastic deformation in titanium alloys.