A novel deformation mechanism in Ti-V binary metastable β-Ti alloys: Deformation kinking promoted by dislocation accumulation

Unlike stress-induced martensitic transformation, deformation twinning as well as dislocation gliding, deformation kinking is an uncommon deformation mechanism in metastable β-titanium (Ti) alloys. In this study, the unique deformation mechanism was reported in Ti-V binary β-Ti alloys for the first time. It was found that a large number of kink bands were distributed in β-grains after cold forging at a strain rate of ~103 s−1. Microstructural characterization manifests that the appearance of kink bands is frequently accompanied by slip bands, whilst dense dislocations are accumulated around the kink bands on a microscopic scale. Such local plastic deformation is quite strong so that the pre-existing athermal ω-precipitates in the initial microstructure is completely destroyed within the kink bands and instead fresh deformation-induced single variant of ω-precipitates is produced. This deformation localization mainly originates from the impediment of dislocation activity caused by both pre-existing athermal ω-precipitates and the intrinsic slip retardation in BCC crystal structures. The deformation kinking is thus suggested to follow a dislocation-based formation mechanism, whilst the resulting Taylor axis of lattice rotation was deduced to be<011>β on basis of extensive crystallographic analysis. These findings enrich fundamental understanding on deformation kinking, and provide helpful information for utilizing the unique deformation mechanism to tune mechanical properties of β-Ti alloys.