Investigation Of the effects Of preheat temperature On Al-5083 Alloy microstructure in welding with GMAW method

Among the Aluminum-Magnesium alloys, 5083 alloy has specific characteristics such as high mechanical features, good weldability, and the most important of all its excellent resistance to corrosion under water. These characteristics caused 5083 alloy to be used widely in the marine industries. One of the welding methods for this alloy, especially suited for thick plates, is GMAW welding method. In welding process of this alloy, in order to eliminate surface moisture and to avoid porosity, lack of fusion and possible distortion, preheat is needed. In this project Al5083-H321 alloy test plates were welded in six different preheat temperatures with GMAW method, using ER5183 filler metal, to investigate the effects of preheat temperature on microstructure. Optical metallugraphy, macrography and scanning electron microscope equipped with EDS, were used to examine the microstructure of this alloy, and also to determinate the effect of changing the preheat temperature on the size of grains, and created precipitations in weld metal and heat affected zone. Finally three kinds of precipitation included precipitations rich in Magnesium (Al-Mg), rich in Iron and Manganese (Al-Fe-Mn) and also precipitations rich in Silicon and Magnesium (Al-Mg-Si) were observed in this alloy. Besides, increasing the preheat temperature caused an increase in the amount of created precipitations and the size of grains and the heat affected zone (HAZ).