Effect of applied stress on formation of ω-phase in β-Ti alloys

Abstract

Since ω-phase crystals in β-Ti alloys formed by aging become nucleation sites of or-phase crystals due to further or high temperature aging, it is thought that this phenomenon can be utilized to produce stronger and more ductile (β+α) duplex Ti alloys. In order to form high density ω-phase crystals, the effects of a stress-aging and hydrostatic pressurizing on the formation of ω-phase crystals in Ti-20Mo and Ti-15Mo-5Zr alloys (mass%) were investigated using high resolution electron microscopy and dark field imaging methods. The results obtained are as follows: (1) An aging under a stress of a half of the yield stress promotes the precipitation of high density ω-phase crystals. (2) Hydrostatic pressurizing also promotes the formation of ω-phase crystals, and it is recognized that a hydrostatic pressure of 0.7 GPa initiates to form ω-phase crystals in a Ti-20Mo alloy.