The ZL114A alloy samples were prepared using vacuum differential pressure casting method.With the help of metallographic microscope

scanning electron microscope and microhardness tester

the effects of graded pressure difference on the microstructure and micro-hardness of vacuum differential pressure casting ZL114A alloy were investigated.The results show that the graded pressure difference significantly affects the microstructure and properties of ZL114A alloy.Within the range of the graded pressure difference of 35 kPa～185 kPa

with the increase of the graded pressure difference

the squeezing ability of molten metal is also enhanced.The primary phase in ZL114A alloy is changed from coarse dendritic crystals to fine resette crystals and equiaxed crystals.The microstructure is obviously refined

and the eutectic silicon phase is changed from coarse rods or needles to fine rods or round grains.Meanwhile

the microhardness of ZL114A alloy has been significantly improved.When the graded pressure difference is 185 kPa

the microhardness reaches 96.9 HV

which is 33.4% higher than that of ones with the pressure difference of 35 kPa.