Dynamic precipitation of Mg2Si induced by temperature and strain during hot extrusion and its impact on microstructure and mechanical properties of near eutectic Al–Si–Mg–V alloy

Dynamic precipitation of Mg2Si and its impact on the microstructures and mechanical properties of Al–12.5 wt% Si–0.6 wt% Mg–0.1 wt% V alloy were studied by applying different extrusion temperatures and extrusion ratios. Optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) observations were used to characterize the microstructure evolution. Tensile properties and the Brinell hardness were tested. Results show that both decreasing extrusion temperature (temperature-induced) and increasing extrusion ratio (strain-induced) of the alloy will result in dynamic precipitation of Mg2Si particles. Dynamic precipitation of Mg2Si leads to a considerable coarsening of the recrystallized grains. Yield strength (YS) and ultimate tensile strength (UTS) of the sample extruded at lower temperature (400 °C) are more than 50% lower than that extruded at higher temperature (540 °C) with the same extrusion ratio of 16. With increasing of extrusion ratio from 16 to 50, both YS and UTS of the samples decrease nearly 30% when extruded at the same temperature of 540 °C.