Friction-stir processing (FSP) has been proven as a successful method for the grain refinement of cast aluminum alloys. The most important attributes of this process are the fine-grain microstructure and characteristic texture, which impart suitable properties in the as-processed material. In the current work, FSP of Al–12%Si alloy has been carried out and the consequent evolutions of microstructure and mechanical properties have been studied. The influence of the tool rotational speed on such characteristics was also evaluated. The results showed that FSP significantly improved the microstructure of the as-cast Al–12%Si alloy by eliminating the porosity and refining both α-Al grains and the Al–Si eutectics. The microstructures favored the improvement of hardness of the processed surface layers, in comparison with those properties of the base material. Finite elements method based, 3D, thermo-mechanical model was built to better-understand the effect of process parameters on temperature gradients.
