Based on Power-Cutoff model

using ProCAST casting simulation software

the die-casting process for magnesium alloy gearbox case at liquidus and semi-solid temperature region was analyzed.By orthogonal experiments

effects of plunger injection speed

casting temperature

mold temperature and the heat transfer coefficient between die mold and die castings on the defect rate were visualized

and the processing parameters were optimized.The results reveal that injection velocity on the maximum defect rate in die casting can be neglected

while lower injection speed can greatly reduce the total casting defect rate with ingate velocity between 40

9

0m/s.Moreover

both the maximum and total casting defect rate can be significantly reduced with semi-solid casting temperature

higher mold temperature and lower heat transfer coefficient between die mold and castings.The optimized processing parameters were presented as follows:the plunger injection speed of 5m/s

pouring temperature of 570℃

mold temperature more than 200℃and heat transfer coefficient between die mold and castings of 500W/（m2·K）.