The effect of hot isostatic pressing on the fatigue behaviour of sand-cast A356-T6 and A204-T6 aluminum alloys

The effect of the hot isostatic pressing (HIP) process on the fatigue resistance of sand-cast A356 (Al–Si–Mg) and A204 (Al–Cu–Mg) aluminium alloys was studied by means of rotating bending tests. Many solidification defects, such as gas pores and shrinkage cavities, were present in both alloys in the sand-cast before HIP. The HIP process had a negligible effect on microstructural features (such as grain size, SDAS, and intermetallic compounds), whereas it significantly reduced the solidification defects. The non-HIP processed A204 alloy showed a slightly lower fatigue resistance than the A356 alloy, due to the presence of many branched shape shrinkage cavities, especially along grain boundaries. For both aluminium alloys, the HIP process led to a reduction in fatigue data scattering and an increase in fatigue resistance, equal to about 40% for A356 and 70% for A204. In the HIP processed condition, when the alloys can be considered pore-free, the A204 showed a 20% higher fatigue resistance than the A356 alloy.