The mechanism of aqueous stress-corrosion cracking of α + β titanium alloys

Abstract

In a previous paper (Cao et al., 2017) [1], a transition in fracture mode in aqueous NaCl Stress-Corrosion Cracking (SCC) of Ti-8Al-1Mo–1V was reported. This paper attempts to unravel the operating mechanism for SCC by dislocation analysis on the Focus Ion Beam (FIB) lift-out foils from pre-crack and the SCC regions. It is shown that both basal <a> and <c+a> slips are operative in the SCC region while the basal <a> is the only activated system in the pre-crack region. Moreover, there is an increase in dislocation density in the SCC region compared to the pre-crack region. Based on these observations, combined Absorption Induced Dislocation Emission (AIDE) and Hydrogen Enhanced Localized Plasticity (HELP) is proposed to be the operating mechanisms for SCC in α+β titanium alloys.