Book Description

This thesis focuses on the friction stir welding (FSW) between similar and dissimilar alloys. FSW is a solid state joining process that welds the work-pieces through a combination of heat generated by friction and mechanical stirring of the metals in the region of the joint. Being a solid state process, FSW can be used to weld alloys with significantly different melting points. This provides a significant benefit over traditional fusion welding process in a variety of applications in automotive, biomedical, aerospace, nuclear and petroleum industries.Two materials - an aluminum alloy (6061-T6, m.p. 582 - 652°C) and a steel (SAE 1018, m.p. 1480°C) are the primary focus of this research. An end mill was modified to perform friction stir welding, and several tool designs made from H13 steel, A2 steel and tungsten carbide were investigated. The tool tilt angle, rotation speed, and travel speed were the primary welding parameters which considered. Rockwell hardness, tension, and 4- point bending tests were conducted to evaluate the mechanical properties of the welded samples as well as the microstructure test.Results show that in the as-welded condition there is a considerable decrease in the strength and hardness of the aluminum alloy in the joint region. This can be attributed to over-aging of the aluminum alloy due to the heat generated by the joining process. However, standard T6 heat treatment restores the mechanical properties of the aluminum -aluminum joint, and improves the mechanical properties of the aluminum-steel joint. This demonstrated the feasibility of FSW for joining both similar and dissimilar metals.