Titanium alloys are available in four varieties: alpha, alpha/ beta, beta and the newer titanium aluminide. Because more alloying elements are being added to the particular grades, these alloys are progressively more difficult to machine.
The Alpha phase of titanium is pure titanium, relatively soft and can be machined at high speeds.This material presents no significant machining problems. However, the material lacks the beneficial properties of the other alloys, primarily strength and flexibility, so its uses are limited.
Alpha/beta alloys are the most common titanium alloys, and Ti-6A1-4V (6% aluminum, 4% vanadium) is used extensively in the aerospace industry, particularly for jet engines. Ti-6A-4V is used to a lesser extent in the medical and chemical industries.
These alloys are moderately difficult to machine, and relatively short tool life can be a problem because alpha/beta chips are difficult to break and are abrasive.
Beta phase titanium alloys do not have the toughness of the alpha/betas, but they are harder and more brittle. They also are more difficult to machine because of the higher percentages of vanadium, molybdenum and chromium with which they are made. Beta phase alloys of titanium are becoming more common, and present serious machining challenges.
Titanium aluminides are very difficult to machine, but they are extremely lightweight and strong. Earlier, a lack of toughness limited their application. However, material science research has addressed their lack of toughness, and applications are beginning to be developed in auto racing engines, where they are used for push rods and valve stems, and in components for jet engines.