FRICTION STIR PROCESSING OF ALUMINUM ALLOYS

Friction stir processing (FSP) is one of the new and promising thermomechanical processing techniques that alters the microstructural and mechanical properties of the material in single pass to achieve maximum performance with low production cost in less time using a simple and inexpensive tool. Preliminary studies of different FS processed alloys report the processed zone to contain fine grained, homogeneous and equiaxed microstructure. Several studies have been conducted to optimize the process and relate various process parameters like rotational and translational speeds to resulting microstructure. But there is only a little data reported on the effect of the process parameters on the forces generated during processing, and the resulting microstructure of aluminum alloys especially AA5052 which is a potential superplastic alloy. In the present work, sheets of aluminum alloys were friction stir processed under various combinations of rotational and translational speeds. The processing forces were measured during the process and the resulting microstructure was analyzed using TEM. The results indicate that the processing forces and the microstructure evolved during FSP are sensitive to the rotational and translational speed. It is observed that the forces generated increase with the increasing rotational speed. The grain refinement was observed to vary directly with rotational speed and inversely with the translational speed. Also these forces generated were proportional to the grain refinement i.e., greater refinement of grains occurred at lower forces. Thus the choice of process parameters especially the rotational speed has a significant effect on the control and optimization of the process