An insight into high-temperature deformation mechanism of magnesium in-situ composite through development of Johnson-Cook and constitutive model

The establishment of deformation mechanisms of Mg-metal matrix composite (Mg-MMC) is important to improve the high-temperature challenging applications. In this present work, an AZ91/TiC + TiB₂ hybrid in-situ Mg-MMC was synthesized, and its deformation mechanisms were studied through a uniaxial hot compressive test at different temperatures and strain rates. The Johnson-Cook (JC) model and constitutive equation were established using experimental stress-strain data. Through the development of JC model, it was revealed that the TiC–TiB₂ particles enhanced the yield strength parameter and increased the activation energy of the in-situ composite compared to the parent alloy. The load-shifting capability and grain refinement were found to be the dominating mechanisms, which effectively restricted dislocation movement during deformation, resulting in improved deformation resilience of the composite. A detailed study of JC model and constitutive equation parameters was analyzed with a focus on their microstructures.