The Plastic Deformation Mechanism in Nano-Polycrystalline Al/Mg Layered Composites: A Molecular Dynamics Study

Understanding plastic deformation behaviour is key to optimising the mechanical properties of nano-polycrystalline layered composites. This study employs the molecular dynamics (MD) simulation to comprehensively investigate the effects of various factors, such as grain sizes, strain rates, and the interlayer thicknesses of the intermetallic compounds (IMCs), on the plastic deformation behaviour of nano-polycrystalline Al/Mg layered composites. Our findings reveal that the influence of grain size on deformation behaviour is governed by the strain rate, and an increase in grain size is inversely proportional to yield stress at low strain rates, whereas it is positively proportional to tensile stress at high strain rates. Moreover, an optimal thickness of the intermediate layer contributes to enhanced composite strength, whereas an excessive thickness leads to reduced tensile strength due to the fewer grain boundaries (GBs) available for accommodating dislocations. The reinforcing impact of the intermediate IMCs layer diminishes at excessive strain rates, as the grains struggle to accommodate substantial large strains within a limited timeframe encountered at high strain rates. The insights into grain sizes, strain rates, and interlayer thicknesses obtained from this study enable the tailored development of nanocomposites with optimal mechanical characteristics.