A study on the stress corrosion cracking susceptibility of friction stir welded Ti-6Al-4V alloy joints

Abstract

The stress corrosion cracking (SCC) susceptibility of a friction stir welded (FSW) Ti-6Al-4V alloy was assessed through the slow strain rate tensile (SSRT) examinations in air and 3.5% NaCl solution at three temperatures of 25 °C, 37 °C and 80 °C. SSRT results showed that FSW deteriorated the SCC behavior of Ti-6Al-4V in all tested conditions. The fractography of the fractured specimens by SEM revealed that a dimpled fracture mode predominated in the failure of the heat affected zone of the FSWed specimens. Also, it was found that increasing the test temperature resulted in decreasing the fracture toughness of the base and weld metals. The microhardness examination of the welded specimen indicated that the stir zone (SZ) showed higher hardness values than that of the heat affected zone (HAZ). This behavior was attributed to the formation of finer and coarser grains in the SZ and HAZ, respectively.