Titanium use in aerospace and medical applications continues to grow. Alpha case formation is a diffusion reaction that occurs at the surface of titanium when processing at elevated temperature in atmospheres containing oxygen, nitrogen, and/or carbon, with oxygen being the prominent element associated with alpha case. Oxygen is solution strengthening at low concentrations, but greatly decreases ductility and forms alpha case at higher concentrations. Thus, alpha case is brittle and has a detrimental effect on part performance and longevity. Higher temperatures increase alpha case depth. Temperatures less than 550°C (1022°F) limit oxygen mobility and keep case depth from increasing. Above 480°C (896°F), air or water vapor will start to produce alpha case.

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