Effects of microtexture and Ti3Al (α2) precipitates on stress-corrosion cracking properties of a Ti-8Al-1Mo-1V alloy

- There is a significant effect of microtexture (or macro zone) on Stress-Corrosion Cracking (SCC) in α + β Ti alloys.
- Most α grains are favourably orientated for basal slip along the path of SCC crack.
- Significantly reduced SCC susceptibility in powder HIPped material results from the elimination of microtexture.
- SCC did not occur after eliminating both microtexture and α2 precipitates.

Effects of microtexture and Ti3Al (α2) precipitates on the Stress-Corrosion Cracking (SCC) properties of Ti-8Al-1Mo-1V (Ti-811) have been investigated using a constant displacement SCC test in 0.1 M aqueous sodium chloride (NaCl) solution. SEM, TEM, and EBSD were employed to characterize microstructure and microtexture. Results reveal that both microtexture and α2 precipitates increase the SCC susceptibility of Ti-811. The SCC propagation direction aligns with microtextured regions, and most α grains were preferentially orientated for basal slip along the SCC crack. SCC susceptibility was eliminated by implementing hot isostatic pressing (HIPping) and post heat-treatment processes through eliminating both crystallographic microtexture and α2 precipitates. Fractography showed that the formation mechanism of the propagation facets could be attributed to Hydrogen Enhanced Localized Plasticity (HELP).

Proposed facet formation mechanism involves Hydrogen Enhanced Localized Plasticity (HELP) in aqueous NaCl SCC for Ti-8Al-1Mo-1V. The black arrow in (b) indicates crack propagation direction.270