Beyond the dynamic Hall-Petch effect: Mechanical twinning for microscopic strain delocalization

Abstract

Mechanically-induced twinning is considered a beneficial deformation micro-mechanism, primarily due to the dynamic Hall-Petch effect arising from grain size refinement through twinning processes. Yet, in alloys where damage initiation is strongly texture-dependent, the orientation change associated with mechanically-induced twinning can also yield advantagenous outcomes. To demonstrate this, we employ high-resolution in-situ microstructure-based digital image correlation (μ-DIC) techniques to investigate strain heterogeneity modulated by the activation of $\left\{10\overline{1}2\right\}$ extension twinning and its macroscopic consequences in a titanium alloy. Our observations reveal the formation of intense strain localization bands due to pyramidal I <c+a> slip activation in the early plasticity regime (ε∼0.01). However, the intensity of these bands diminishes as $\left\{10\overline{1}2\right\}$ twins nucleate and propagate. As deformation progresses, the strain distribution becomes more uniform across the microstructure, attributed to strain delocalization effects caused by twin propagation. Quantitative damage analysis suggests that strain delocalization by $\left\{10\overline{1}2\right\}$ twin activation can enhance microstructural damage resistance.