Semi-solid isothermal heat treatment combined extrusion is a key method to strengthen mechanical properties of magnesium alloys by improving its structure.In this paper,the effect of holding temperature and time on the grain size,morphology and liquid fraction of Mg-15Gd-1.7Ni magnesium alloy microstructure are studied.Microstructure and hardness of Mg-15Gd-1.7Ni alloy are analyzed under direct extrusion in the as-cast state,semi-solid extrusion and water-quenched semi-solid extrusion.The results show that the grains of the α-Mg phase in the semi-solid heat treatment of magnesium alloy become fine,rounded and evenly distributed,and the composite extrusion process improves the inhomogeneity of hardness in the direction of vertical extrusion and extrusion.
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