Phase Diagrams
Titanium Alloys

· Titanium alloys are important for high temperature applications. The Al-Ti binary diagram shown indicates the 1672 C melting point of pure Ti.
· At 883 C, pure Ti undergoes a structural phase transition. The α-phase has an HCP structure, and the high temperature (β-Ti) -phase is BCC
· Addition of small quantities of aluminum to the alloy increases the temperature of the 
a -> β transition. For a Ti- 6 wt % Al alloy (green line on diagram) the transition temperature has increased to 1000 C.

From: Smith, Structure and Properties of Engineering Alloys, McGraw Hill (1981)