One-step aging of A357 alloy produced by low pressure casting and by counter pressure casting

Effects of different artificial aging at 150, 165, 180 and 200°C for different time on hardness of A357 alloy specimens produced by low pressure casting and by counter pressure casting were evaluated. The results reveal that the hardness difference between the specimens produced by low pressure casting and by counter pressure casting can be neglected, however, hardness of the specimens produced by counter pressure casting exhibits more uniform distribution. The hardness of the two specimens is decreased by approximately 20% after solid solution. However, after artificial ageing, hardness of the specimens produced by counter pressure castings is higher than that produced by low pressure casting. In addition, the specimens produced by low pressure casting is different from counter pressure castings in hardness change with the time change at 165°C and 200°C.