Effect of microstructure on fatigue behaviour of cast Al-7Si-Mgalloy

The fatigue behaviour of a cast Al-7Si-Mg alloy, conforming to A356, has be en studied, Specimens of this material were tested in both the as cast cond ition and a solution treated and aged condition. It was observed that the s ize, number, and position of casting defects influenced the fatigue life ve ry strongly. This marked effect nearly hides that of the heat treatment, Ne vertheless, if the analysis is carried out considering only results obtaine d from sound specimens it is revealed that the heat treatment causes an imp rovement in the fatigue resistance of the alloy.