The rotating-rod induced nucleation（RRIN）was adopted to fabricate the semi-solid slurry of A356 alloy

and influence of holding time on the microstructure of A356 aluminum alloy semi-solid slurry was investigated.The results show that

with the increase of holding time

the primary phase size is increased gradually

however

the shape factor of the primaryα-Al is decreased firstly and then increased

which follows the Oswald ripening mechanism.With holding for 1min

the equivalent diameter of the primary phase is about 54μm with shape factor of 0.89

while the number of particles per unit area is about 175/mm

2

.With the holding time of 5min

the primaryα-Al shape factor is 0.83

and its equivalent diameter reaches about 74μm

and number of particles per unit area is about 130/mm

2

.However

the shape factor reaches the largest with the holding time of 20 min

as much as 0.97

and the number of particles per unit area is about 70/mm

2

.