Slip- and Twinning-Related Dissipation in AZ31B Magnesium Alloy

Abstract

Energy conversion in AZ31B magnesium alloy depends strongly on the dominant deformation mechanism. In slip-dominated specimen, strained parallel to extrusion direction $\parallel$ ED, approximately 50$\%$ of plastic work is converted into heat, with Taylor-Quinney coefficient $β_{int}$ rising rapidly then gradually with strain. Twinning-dominated specimen ($\perp$ ED) initially stores most plastic work, showing minimal heat dissipation, reflecting the dislocation-mediated nature of twinning in HCP metals, and $β_{int}$ increasing to $\approx$ 0.4 at failure. The final microstructure tracks stored energy evolution: the $\parallel$ ED specimen, predominantly slip-dominated, exhibits fragmented grains and strong dislocation activity, with twinning appearing at the final stages, driving energy accumulation and lattice rotation. In contrast, the $\perp$ ED specimen shows limited refinement, early localization, and twinning-driven premature fracture.

Figures (4)

• Figure 1: Specimen placement and initial microstructure (a) along with the experimental setup for heat sources determination and specimen dimensions (b).
• Figure 2: Stress-strain curves for slip-dominated ($\parallel$ ED) and twinning-dominated ($\perp$ ED) loading directions, with the corresponding strain hardening coefficients ${d\sigma}$/${d\varepsilon}$ and mean temperature changes $\Delta T_{mean}$ (a). Corresponding fracture surfaces (b) and the distributions of the axial component of Hencky strain rate $\dot{\varepsilon}_{yy}$, and temperature gradient $\nabla_{y} T$ (c).
• Figure 3: Plastic work $w_p$, energy dissipated as heat $q_d$ and stored energy $e_s$ as functions of plastic strain for slip-dominated ($\parallel$ ED) (a) and twinning-dominated ($\perp$ ED) specimens (b), along with the corresponding evolution of the integral $\beta_{int}$ and differential $\beta_{diff}$ Taylor-Quinney coefficients (c).
• Figure 4: Microstructure after deformation shown as inverse pole figures projected along the straining direction along with pole figures evolution, for specimens strained ($\parallel$ ED) (a) and ($\perp$ ED) (b).