Effect of Tool Pin Geometry on the Microhardness and Surface Roughness of Friction Stir Processed Recycled AA 6063

Abstract

Friction stir processing was experimented on recycled aluminum alloy 6063 to investigate the effects of varying friction stir tool pin geometry and friction stir processing parameters on the microhardness and surface roughness. Different tool pin geometry has great influence on the outcome as it alters the ability to provide localized heating and better material flow. This study was performed using two different types of tool pin geometry, namely, the cylindrical threaded and the taper threaded pins, across varying rotational speeds and feed rates. The mechanical properties of the processed workpiece were inspected and analyzed in terms of microhardness, microstructure, and surface roughness. The results show that the taper threaded tool offers the highest improvement in microhardness up to 63% at the lowest rotational speed and highest feed rate at 1150 rpm and 30 mm/min, respectively, and this is supported by microscopy images showing finer grains with the compact and homogenous distribution. The taper threaded tool also provided a better surface roughness than the cylindrical threaded tool. However, the surface produced by cylindrical threaded at 30 mm/min feed rates is as smooth and consistent as that of taper threaded tool.

Keywords

• friction stir processing
• high speed steel
• recycled aluminum alloy 6063
• tool pin geometry
• surface roughness
• microstructure