The Role of Twinning Deformation on the Hardening Response of Polycrystalline Magnesium from Discrete Dislocation Dynamics Simulations
JOHNS HOPKINS UNIV BALTIMORE MD DEPT OF MECHANICAL ENGINEERING
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The deformation of micro-twinned polycrystalline magnesium Mg was studied using three-dimensional discrete dislocation dynamics DDD. A systematic interaction model between dislocations and 10 1-2 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 GBs 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.
- Inorganic Chemistry