Alpha case

In metallurgy, alpha case is the oxygen-enriched phase that occurs when titanium and its alloys are exposed to heated air or oxygen. Alpha case is brittle, and tends to create a series of microcracks which will reduce the metal's performance and its fatigue properties. Alpha case can be minimized or avoided is by processing titanium at very deep vacuum levels. However once present on the surface, the only way to remove Alpha case is by the subtractive methods of machining and /or chem milling.