Effects of pouring temperature and grain refiner （Al-5Ti-1B）addition on microstructure of semi-solid A356 alloy billets prepared by compound process of low temperature pouring and grain refining were investigated. The results show that with decreasing pouring temperature from 715℃ to 635℃

primary Al phase is transformed from dendrite into rosette structure and then into equiaxed one

where grain size is refined and spheroidized with decreasing in the pouring temperature. However

with decreasing pouring temperature to 615℃

grain exhibits coarse and un-even. At a given pouring temperature

grain size is refined with increasing in grain refiner addition

however

the refining effects are gradually fade as the pouring temperature decreases. Grain size and morphology change can be ignored with adding grain refiner at below 635℃.Optimized processing parameters are as follows: pouring at 635

6

55℃ and 0.1%

0

.2% grain refiner addition.