Microstructural Characterisation of Friction Stir Processed Cast AlSi9Mg Aluminium Alloy

Aluminium alloy castings become more popular when a refined microstructure and a uniform distribution of Si particles are easily produced. One of the technologies that can fulfil these requirements is Friction Stir Processing (FSP). Therefore, the formation of various microstructural regions during FSP of AlSi9Mg alloy has been studied. It is presented that each of the regions are characterized by unique microstructures. Prior to FSP, the microstructure of a representative as-cast aluminium alloy was composed of Al dendrites and a nonuniform distribution of Si and Fe. FSP microstructurally modified and significantly refined the as-cast material, effectively eliminating the microstructural segregation and porosity of the base material. The characteristic microstructures are reflected in the hardness distribution. The hardness of the modified area was different from the base material.