Local Fatigue Crack Propagation Resistance Relevant To Microstructure Uniquely Developed In A Friction Stirred Ti-6Al-4V Alloy Joint

Abstract

The local resistance to fatigue crack propagation (FCP) in a friction stir welded (FSWed) Ti-6Al-4V alloy joint was investigated, by extracting the miniature CT specimens. Special attention was paid to the role of specific microstructures developed accompanying with a transformation induced lamellar structure (TILS) during the stirring process. Experimental works indicated that the FCP rates were higher in the stirred zone, especially in the coarse TILS zone which consisted of the prior non-transformed duplex structure and the beta-transformed coarse structure, compared with those in the base metal. These backgrounds were discussed on the basis of fracture mechanics with Reference to the measurement of residual stress.