Effect of Isothermal Time on Mg-9Zn-2Al Magnesium Alloy Semi-Solid Slurry Prepared by Self-Inoculation Method

Semi-solid slurry of Mg-9Zn-2Al magnesium alloy has been prepared online by self-inoculation method(SIM). The effect of isothermal time on semi-solid microstructure evolution has been investigated with isothermal temperature 585℃. Results showed that with isothermal time prolonging, the grain has been with a process of firstly being spheroidized and then mutilated and continuous to grow. An ideal isothermal time should be limited to 4~8min for average grain size of 47.5~48.8μm with roundness between 1.2 and 1.3. In isothermal process,Microstructure evolution mainly had three stages including high melting particle precipitation and transient nucleation at smaller undercooling, and grains continuous growing because of magnesium atoms cumulation on the primary phase, and coalescence and growing of α phase.