Creep Behaviour of Hot Isostatically Pressed Metal-Matrix Composite

Castings usually contain defects such as shrinkage cavities and internal gas porosity. The application of hot isostatic pressing (HIPping) to cast metals can remove such defects through the synergistic effect of high isostatic pressure and high temperature. This paper investigates the effects of HIPping on creep of cast A359/SiC/20p composite. Although creep life was expected to improve due to removal of internal porosity in the castings, the creep results were contrary to expectations. Activation energy calculated for the cast composite, showed a decrease in activation energy for the material after HIPping. Creep life was noted to have improved with higher tensile strength as for the cast composite while creep strain at failure improved with an increase in elongation for the cast-HIPped composite. The effect of stress on creep properties are reported to show a decrease in creep life and creep strain at failure with an increase in stress, temperature remaining constant.