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

F Gao and Q Yang and JG Du and G Jiang, JOURNAL OF MOLECULAR MODELING, 26, 103 (2020).

DOI: 10.1007/s00894-020-04361-0

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 x 10(9) s(-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 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.

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