Effects of α phase precipitation on crevice corrosion and tensile strength in Ti-15Mo alloy

The effects of the α phase precipitation on the crevice corrosion at 373 K and the tensile properties at ambient temperature were investigated in the Ti-15Mo alloy. Relatively coarse α phase precipitates with the depletion of Mo formed in the alloy after aging at 873 K. The aged alloy maintained high crevice corrosion resistance in the 10% NaCl water solution with a pH value of 0.5 at 373 K, and showed much higher yield strength than that of the solution treated alloy. This increase in yield strength was mainly attributed to the change in the deformation mode of the β phase from the {332}〈113〉 twinning to the slip caused by the enrichment of Mo in the β phase, and contributions of the precipitation/dispersion hardening and the grain refinement strengthening are negligible. The yield strength decreased with an increase in the volume fraction of the α phase since the α phase is softer than the β phase which was confirmed by nanohardness measurements.