Effects of Friction Stir Welding on Microstructure and Mechanical Properties of Extruded Secondary Aluminum 6061 Alloy

Abstract

Experiments were carried out to determine the effects of friction stir welding on microstructure and properties of recycled Aluminum 6061 alloy, whose alloy content varied from that of primary alloy. The alloy was processed at tool speed and feed ranges of 530 rev/min–1320 rev/min and 40 mm/min–100 mm/min respectively. Microstructure examination; tensile test and Vickers microhardness evaluation were carried out. Microstructure of the alloy was in four zones including: base metal, heat affected zone, thermo-mechanically affected zone and stirred zone. Average grain size of unprocessed material was 93 μm. Processing the alloy at 530 rev/min and 100 mm/min resulted in grains of average size 93 μm, 183 μm and 7 μm; in base metal, heat affected zone and stirred zone respectively. Tensile failure occurred in heat affected zone; that was exposed to high heat. The alloy hardness decreased to a minimum in heat affected zone, followed by a brief rise in thermo-mechanically affected zone, to another maximum in stirred zone. Processed zone hardness was inversely proportional to tool speed and directly proportional to feed rate. Increase in the speed and decrease in feed, increased heat which deteriorated the properties.