Stress Corrosion Cracking Mechanism of Ti-6Al-4V in Acidic Methanol

Abstract

Stress corrosion cracking of in acidic methanol at anodic potential has been studied. The specimen surface morphology was examined as a function of strain rate, electrode potential, water content, and heat treatment. Depending on the test conditions, two kinds of cracks can be formed: those along the slip traces and those perpendicular to the applied stress. A new model is proposed to explain the initiation of these cracks. The cracks along the slip traces result from preferential dissolution of moving dislocations along the slip planes. Rupture of the material between these cracks results in the perpendicular cracks.

Observations of Facet Formation in Near-α Titanium and Comments on the Role of Hydrogen

“…Furthermore, no faceted initiations were observed that seemed to be the result of surface slip band extrusions like those reported by Zhang and Vereecken. [40] There was one small region of facets ( Figure 14) that was within a few microns from the surface of the specimen whose features indicated that the crack was running away from the surface of the specimen. This suggests that these facets were formed at a small crack length after surface initiation in grains not suitably oriented for faceted crack propagation.…”

Stress corrosion cracking (SCC) and hydrogen-assisted cracking in titanium alloys

“…A new twist to the anodic dissolution process has been provided by certain plastic events reported (Zhang and Vereecken, 1990;Gao et al, 2000). In Ti-6Al-4V alloys, SCC studies in methanol revealed secondary cracks along slip traces indicating a preferential dissolution along slip planes.…”

Fracture Surface of a Ti-6Al-4V Specimen with EDM Notches Tested under Quasi-Static Loading in Methanol

“…Ti-6Al-4V is for example susceptible to Stress Corrosion Cracking (SCC) in maritime conditions [4] and in methanol and methanol-HCl solutions [5]. The detrimental effects of methanol on two Ti-6Al-4V Apollo service propulsion system pressurized fuel tanks were observed in [6]. However, 1% of moisture in methanol or cathodic protection can prevent SCC.…”