Effects of processing parameters on microstructure and mechanical behaviors of underwater friction stir welding of Al5083 alloy

摘要

In this work, friction stir welding (FSW) of Al5083 alloy under various processing parameters was performed and effect of welding environment (water and air) on the microstructure and the mechanical properties was investigated. The results showed that water environment led to a high cooling rate so that the grains did not have enough time to grow and as a result, the heat affected zone (HAZ) disappeared in the water-cooled specimen with rotational speed of 600 rpm and welding speed of 30 mm/min. Moreover, existence of peak values of temperature in the stir zone (SZ) made changes in the microstructure so that the size of grains and precipitates were totally different for each sample. Compared to the air-cooled welded sample, the increase in the tensile strength of water-cooled specimens may be due to the increase of hardness in the stir zone caused by a fine grain structure. It also revealed that the hardness value in the stir zone of water-cooled specimens Was much higher than that of the sample cooled in the air. Considering the same welding parameters for the air and water cooled specimens (rotational speed of 600 rpm and welding speed of 30 mm/min), the hardness value increased by 25% in the stir zone. (C) 2016 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.