Microstructure and mechanical properties of as-cast and wrought Mg–Ni in-situ formed alloys

The effects of nickel addition to magnesium in the hypoeutectic range were investigated in the as-cast and extruded conditions. At low Ni content of 5 wt-%, the grain-boundary eutectics were present in the grain refined α-Mg matrix; while at high Ni content of 15 wt-%, the eutectic constituent became the matrix of the alloy with the appearance of α-Mg rosettes. The addition of Ni up to 15 wt-% led to a significant enhancement of the strength-ductility balance. Moreover, the formation of long Mg 2 Ni particles at the boundaries of eutectic colonies was explained based on the cooling curve thermal analysis results. Furthermore, remarkable grain refinement by dynamic recrystallisation (DRX) and fragmentation/dispersion of intermetallic particles during hot extrusion led to the improvement of tensile strength, ductility, and toughness.