Effect of oxygen and hydrogen on mechanical properties of commercial purity titanium

Commercial purity (CP) titanium is used primarily in applications requiring exceptional corrosion resistance. The CP titanium alloys contain small amounts of oxygen. The mechanical properties of titanium, such as tensile and fatigue strengths, can be enhanced with oxygen additions, but care must be taken not to compromise toughness and ductility. Hydrogen, at concentrations below the commercially accepted limit, can also be detrimental to some of the mechanical properties of CP titanium, particularly under multiaxial stress and at both high and low strain rates. Hydrogen decreases ductility and creep resistance without, however, lowering the tensile strength. Although some of these effects result from the formation of a hydride phase, transmission electron microscope evidence indicates that residual interstitial hydrogen lowers the energy for dislocation generation and propagation. These hydrogen effects are more pronounced in oxygen alloyed titanium than in high purity titanium.