Effect of holding pressure on the microstructure of vacuum counter-pressure casting aluminum alloy

The effect of holding pressure on the microstructure of vacuum counter-pressure casting aluminum alloy was analyzed by observing the changes of the Si phase size and alloy density. The results show that with the increasing of holding pressure of vacuum counter-pressure casting, the extrusion and infiltration ability among dendrites is enhanced and the microstructure of prepared alloy samples at the same location becomes finer, more uniform and denser. Under the same holding pressure, the smallest extrusion and infiltration ability takes place at the middle of sample. Accordingly, from the pouring gate to middle, the microstructure of vacuum counter-pressure casting aluminum alloy sample becomes coarser, more non-uniform and less dense, while the microstructure from the middle to top becomes finer, more uniform and denser.