EFFECT OF OXYGEN AND HYDROGEN ON MECHANICAL-PROPERTIES OF COMMERCIAL PURITY TITANIUM

Commercial purity (CP) titanium is used primarily in applications requ iring 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 addition s, but care must be taken not to compromise toughness and ductility. H ydrogen, at concentrations below the commercially accepted limit, can also be detrimental to some of the mechanical properties of CP titaniu m, particularly under multiaxial stress and at both high and low strai n rates. Hydrogen decreases ductility and creep resistance without, ho wever, lowering the tensile strength. Although some of these effects r esult from the formation of a hydride phase, transmission electron mic roscope 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 pu rity titanium. (C) 1996 The Institute of Materials and ASM Internation al.