Thermomechanical Analysis of Friction Stir Welding of Dissimilar Aluminium Alloys

Abstract

Friction stir welding (FSW) is a relatively new welding process where a rotating non consumable tool is used to join similar and dissimilar material through stirring action and plastic deformation. The objective of the present work is to develop a thermo mechanical model for dissimilar FSW. Literature review has been carried out to know the status of the work on FSW of dissimilar aluminum alloys. Thermal modelling has been developed to obtain the peak temperature during welding process. Temperature can help in predicting the thermal residual stress generated during welding process. Thermal and thermo mechanical numerical models have been validated with existing literature data. The focus of this research is to predict temperature and residual stress of the materials AA6061-T6 and AA2014-T6 during FSW. Experiments have been carried out for butt joining of AA6061-T6 and AA2014-T6 to obtain thermal histories and temperature distribution in work piece during air and immersed FSW. To measure the temperature histories at various location during FSW, K-type thermocouples have been inserted in the mid thickness of the plate at AS and RS. Regression analyses by the least squares method has been carried out to predict the temperatures at the joint line. Thermo mechanical numerical model has been developed in ABAQUS for FSW of dissimilar materials namely AA6061T6 and AA2014-T6 for prediction of temperature and residual stress in air and immersed conditions. Experimental results of peak temperatures have been compared with simulated results. The experimental results and simulated results are found in good agreement with each other. It has been observed that less residual stresses in transverse direction in comparison to longitudinal direction. The effect of water on temperature, mechanical properties and residual stresses have been studied during FSW of dissimilar materials. In Immersed FSW values of the temperature and residual stresses are found lower and values of the micro hardness are found higher compared with air FSW.