Strain rate-induced plasticity in bcc β-Ti alloy single crystal micropillars containing brittle ω-precipitates

Brittle omega-precipitates in bcc beta-Ti alloys are well known to dramatically degrade material plasticity and even trigger macroscopic premature fracture, posing an obstacle for structural applications. The embrittlementmechanism is intimately related to dislocation pile-up at the omega/beta interface that leads to stress concentration and undesirable failure. The underlying physics of improving ductility remains to be further uncovered. Herewe report a new finding in beta-Ti alloy single crystal micropillar compression that the plasticity can be substantially improved bymeans of increasing strain rate, while mechanical strength simultaneously exhibits striking "faster is stronger" fashion. The results reveal that the improvement of micropillar plasticity upon higher loading rate can be ascribed to the wider deformation band, in contrast to equivalents under quasi-static mode. The microscopic examination shows that cross slip induced by screw dislocations governs the plasticity improvement, which is further validated by crystallographic analysis and first principle energy landscape calculations. This "dynamic self-toughening" behavior advances our fundamental understanding to the plastic deformation mechanism of omega-precipitate contained bcc beta-Ti alloys. (C) 2017 Elsevier Ltd. All rights reserved.