Atomistic investigation on effect of Ca doping ratio on mechanical behaviors of nanocrystalline Mg-Ca alloys.

Abstract

The effects of doping ratio of calcium (Ca) on mechanical behaviors are investigated using molecular dynamics (MD) and the second nearest-neighbor modified embedded-atom method (2NN-MEAM) formalism for nanocrystalline (NC) Mg-Ca alloys system. Research results indicate that mechanical behaviors of Mg-Ca alloys are independent of lower strain rate (under 1.0 ×109s-1). In addition, we observe that Ca doping can affect the mechanical properties of the Mg-Ca alloys, and the optimal 2.0 at% of Ca atoms, which has excellent plasticity, is revealed. When the doping ratio is lower than critical atomic percent (CAT) of Mg2Ca, Young's modulus and yield stress decrease increasing at% of substitutional Ca. The pyramidal <c + a > dislocations are observed frequently at more active grain boundary (GB) with higher Ca doping ratios. In contrast, with doping ratio above CAT, Mg2Ca reinforcement dominates brittleness Mg/Mg2Ca nanocomposites to obtain high strength. By calculating, a significant increase of strength is discovered when at% of Mg2Ca is above 18.85 (5.34 at% Ca). Intergranular fractures are more likely to nucleate and propagate along weaker Mg/Mg2Ca interfaces. These results are instrumental in design and improving the mechanical properties of Mg-Ca alloys.