Abstract
Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI, initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry due to the extremely high strength-weight ratio together with good corrosion resistance properties. Welding of titanium alloys by traditional fusion welding techniques presents several difficulties due to high material reactivity resulting in bonding with oxygen, hydrogen, and nitrogen with consequent embrittlement of the joint. In this way FSW can represent a cost effective and high quality solution. In the paper the effect of the tool rotational speed on welding temperatures acquired during FSW of the widely commercially diffused Ti-6Al-4V alloy is analyzed. Experimental results are correlated to the mechanical and metallurgical properties of the obtained joints. The study of the temperatures reached leads to a deeper knowledge of the process as well as to the possibility to predict the microstructural evolutions occurring during the weld and dramatically influencing the mechanical properties of the obtained joints.