Recrystallization mechanisms, grain refinement, and texture evolution during ECAE processing of Mg and its alloys

An efficient temperature-dependent crystal plasticity framework for pure magnesium with emphasis on the competition between slip and twinning

“…Their temperature dependence, however, has remained an open question. Wonsiewicz and Backofen (1967) observed an increasing amount of CTs in their single-crystal experiments at higher temperatures, whereas Barnett (2007), Barnett et al (2008), Kecskes et al (2021), Chakkedath et al (2018) noted a reduced propensity for twinning and especially for CT with increasing temperature. To accommodate deformation along the 𝑐-axis of the crystal, the material must exhibit some deformation mode(s) with a 𝑐-component in the Burgers vector.…”

“…Due to the reduced activation stresses on these systems, at elevated temperature, pyramidal and prismatic slip accommodate a larger portion of the plastic deformation. This leads to a smaller relative contribution of basal slip and twin systems to accommodate the overall deformation (Barnett, 2007;Kecskes et al, 2021;Nie et al, 2020). Hence, a strong temperature dependence of the non-basal slip systems was inferred, whereas, surprisingly, it was found that basal slip as well as TTs show little to no change in behavior with increasing temperature and are often assumed to be virtually temperature independent (Chapuis and Driver, 2011;Nie et al, 2020).…”

“…Upon reaching a critical twin volume fraction, the twin is considered saturated and set to be fully reoriented. This leads to strain hardening (Kecskes et al, 2021) (due to twin boundary and geometric hardening, while the Basinski effect leads to the transformation of glissile into sessile dislocations (Knezevic et al, 2010;Basinski et al, 1997)). As we do not resolve twins spatially nor account for the formation of twin lamellae (such as, e.g., in the composite grain model of Proust et al (2007)), these effects are condensed into a single hardening parameter 𝑐 𝛼 , applied upon twin saturation.…”

“…These shortcomings (and others, see e.g. Nie et al (2020), Kecskes et al (2021) or Eswarappa Prameela et al ( 2021)) have prevented the wide-spread use of Mg alloys in industry.…”

“…Although we focus on pure Mg in this study, data for pure Mg is scarce, so that widely available data for Mg alloys is consulted, where required. For more exhaustive reviews, we refer to Nie et al (2020) for a discussion of microstructure and properties of wrought Mg alloys, Sitdikov and Kaibyshev (2001) for a review of thermal and recrystallization effects in Mg and Mg alloys, and Kecskes et al (2021), who provided a recent compilation of findings.…”