Effects of processing parameters and addition of flame-retardant into moulding sand on the microstructure and fluidity of sand-cast magnesium alloy Mg-10Gd-3Y-0.5Zr

In this study, the effects of processing parameters (such as pouring temperature and mould pre-heating temperature) and flame-retardant content on the microstructure and fluidity of sand-cast magnesium (Mg) alloy Mg-10Gd-3Y-0.5Zr (GW103K) were systematically investigated. It was found that the increase of pouring temperature leads to coarsened microstructure and decreased fluidity of sand-cast GW103K alloy. Increase of mould pre-heating temperature incurs coarsening of as-cast microstructure and increase of fluidity. The addition of flame-retardant into moulding sand has a negligible influence on the microstructure of sand-cast GW103K alloy. With the increase in flame-retardant content, fluidity of the alloy initially increases and then decreases. The optimized process parameters and flame-retardant addition were obtained to be pouring temperature of 750 °C, mould temperature of 110 °C, and flame-retardant addition of 1%. The fire retardant mechanism of moulding sand was determined.