The Effects of Oxygen in Beta Titanium Alloys

The effects of increasing oxygen content on alpha, alpha-beta, and commercially pure titanium alloys are generally well understood and reported in literature.  As oxygen levels are increased above a critical level, alpha-2 formation and slip planarization result in decreased ductility, formability, and resistance to crack propagation. As a result of this understanding, oxygen maximums around 0.2 wt% or less have been established for most common titanium alloys.   

The mechanisms and effects of oxygen in beta titanium are much less understood.  Beta titanium alloys are dominated by the BCC phase and thus not necessarily subject to the same alpha-2 formation and subsequent slip planarization observed in alpha, alpha-beta, and commercially pure titanium alloys.  The chemistry specifications for most beta titanium alloys, however, set the oxygen maximums at levels similar to alpha, alpha-beta and CP titanium alloys.   This work explores the effects of oxygen on the mechanical properties and microstructure of two beta titanium alloys, ATI 5553™ Alloy (Ti-5Al-5V-5Mo-3Cr) and ATI 15Mo™ Alloy.