The role of twinning deformation on the hardening response of polycrystalline magnesium from discrete dislocation dynamics simulations

Abstract

The deformation of micro-twinned polycrystalline magnesium (Mg) was studied using three-dimensional discrete dislocation dynamics (DDD). A systematic interaction model between dislocations and f1 0 1 2g tension twin boundaries (TBs) was proposed and introduced into the DDD framework. In addition, a nominal grain boundary (GB) model based on experimental results was also introduced to mimic the GB's barrier effect. The current simulations show that tension TBs act as strong obstacles to gliding dislocations, and contribute significantly to the overall hardening response, while twin growth results in a softening effect. Therefore, the Mg concave stress-strain curve can be explained in terms of the competition between TB induced hardening and twin growth induced softening. At low strain levels, twin growth induced softening dominates and a decreasing hardening rate is observed in Stage-I. In Stage-II, the TB induced hardening dominates, which leads to an increasing hardening rate.

Towards resolving the anonymity of pyramidal slip in magnesium

“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) magnesium, which is of great importance for discrete dislocation dynamics [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] and crystal plasticity [33] simulations.…”

“…Molecular dynamics (MD) simulations have showed that during c-axis compression and tension, 〈c þa〉 dislocations predominantly nucleate on Pyramidal-I planes from free surfaces and cavities [13][14][15], while discrete dislocation dynamics (DDD) simulations support Pyramidal-II slip [16][17][18]. On the other hand, the transition of slip from Pyramidal-I to Pyramidal-II planes was shown to be plausible through cross-slip or cooperative slip at high applied stresses [13].…”

Hardening and softening analysis of pure titanium based on the dislocation density during torsion deformation

“…However, the tension twin {10-12} played a hardening role in magnesium alloy [21]. Moreover, the interaction between slip and twinning had an important effect on hardening and softening for HCP metals [18,22,23].…”

Quantifying the effect of hydrogen on dislocation dynamics: A three-dimensional discrete dislocation dynamics framework

“…Over the past two decades, DDD simulations have been employed successfully to study many aspects of dislocationmediated plasticity in metals (e.g. [8,14,19,13]), and by incorporating the effect of H into this framework, many aspects of the HE problem can be effectively studied.…”