Effect of oxygen addition on the formation of isothermal ω phase in Ti-Fe alloys

Abstract

The effect of the addition of oxygen on the formation of microstructure cooled from the β phase of Ti-Fe alloy was examined. The alloy ingots of Ti-(4, 5, 6, 7, 8, 9 and 10) at.% Fe and Ti-8 at.% Fe-(1 and 3) at.% O were arc-melted. They were homogenized at 1200 °C for 3.6 ks and then hot-rolled at 850 °C into 1.5-mm thick sheets. The disk specimen was fabricated and then put in the differential thermal analysis (DTA) apparatus. The disk in the DTA was heated at 1000 °C for 0.6 ks in the β phase and then cooled to room temperature at a rate of 50 °C/min. The microstructure was examined by an optical microscope after the DTA experiment. In the Ti-(7 and 8) Fe alloys the ω phase formed during cooling. The addition of oxygen in the Ti-8Fe alloy promoted the β→α transformation. Furthermore, the addition of one at.% oxygen in the Ti-8Fe alloy promoted β→ωi transformation, while the addition of three at.% oxygen suppressed the β→ωi transformation during cooling.

The effects of oxygen addition on microstructure and mechanical properties of Ti-Mo alloys for biomedical application

“…The oxygen addition suppressed the martensitic transformation of β→α' and α" phase ( Kawano et al, 2019 ). It is interesting to note that oxygen addition suppressed the β→athermal ω phase transformation during quenching while it accelerated the β→isothermal ω phase transformation during slow cooling ( Kobayashi et al, 2020a ) or isothermal holding ( Niinomi et al, 2016 ). Examined the effects of oxygen or nitrogen addition on the age-hardening and spinodal decomposition of α′ or α" phase in Ti-4Mo ( Saeki et al, 2018 ) and Ti-10V-(0, 1, 3)O or N alloys ( Kobayashi et al, 2020b ).…”