Influence of Parameters and Tool Geometry on Friction Stir Processing of Aluminum-Cerium Alloy

Abstract

The objective of this study is to address the challenges of improving the mechanical properties of an Aluminum-Cerium-Magnesium (Al-Ce-Mg) alloy through friction stir processing (FSP). The Al-Ce-Mg alloy has promise as an economical and effective high-temperature structural alloy. However, casting the alloy results in a heterogeneous distribution of strengthening intermetallics and casting porosity that do not achieve mechanical properties this alloy system is capable of. FSP has proven to improve alloys similar to Al-Ce-Mg by breaking up intermetallics, homogenously redistributing their refined particles, and closing casting porosity. Nonetheless, friction stir processing is a recently developed manufacturing process that remains to be fully understood, and results vary based on utilized machinery and the chemistry of the material being processed. Therefore, this study investigated the processing parameters of rotational speed, traverse speed, and tool geometry for FSP of one Al-Ce-Mg alloy. A relationship between rotational and traverse speed with material flow was observed. Additionally, knowledge was gained about the interaction of the material with the tool. Further, varying the tool geometry showed potential for significant improvement of material flow and processing conditions. By altering the tool geometry, it was observed that the maximum processing force was reduced by up to 2000 N. The collective evidence of this study shows that FSP can successfully improve the near-surface properties of Al-Ce-Mg alloys and process improvements exist that can reduce the required process forces.