Friction Stir Welding of Thick Aluminium Welds-Challenges and Perspectives

The present paper describes the main challenges faced by the heavy metal industries in the adoption of the friction stir welding of thick section. The requirement of higher forge axis load necessitates the use of a massive and expensive FSW machine, powerful fixtures and improved tool material technology to withstand the higher bending stresses. The thicker sections are also responsible for the significant variations in the joint properties such as grain size, precipitates morphology, distribution of secondary phase particles and hardness due to the noticeable differences in the temperature distribution along the weld thickness. To address these typical challenges in the friction stir welding of thicker sections, a preheating technique along with a composite backing plate is developed. The main advantages of the present approach are to reduce the requirements of the higher forge axis load, power consumption of the FSW machine, tool wear, and improved weld productivity and joint properties through a thermal balance along the thickness of the weld. The present approach can also be extended to the thicker plates of the high strength materials.