Classification of Titanium Alloys

The microstructure is a method used to classify titanium alloys. The structure of these types of titanium alloys depends on the alloy composition and process used to make them.

Alpha Alloys

Alpha alloys are titanium alloys that are only purposely alloyed with oxygen. While other components such as carbon and iron can be found in small quantities, they only exist as impurities. As an interstitial alloying element, oxygen significantly boosts strength while decreasing ductility. The chemical and engineering industries are the primary users of alpha alloys.

Here, great corrosion behavior and deformability are more important than high (specific) strength. The main difference between commercially pure (cp) titanium grades is their oxygen concentration.

Near-Alpha Alloys

Near-alpha alloys of titanium are the most common high-temperature alloys. This alloy class is appropriate for high temperatures because it combines the superior creep behavior of alpha alloys with the high strength of alpha + beta alloys. However, their maximum working temperature is now limited to 500 to 550 ºC.

Beta and Near-Beta Alloys

Beta alloys are another type of titanium material. Manufacturers create all titanium alloys by adding enough beta-stabilizing elements to titanium. These materials have been available for many years but have only lately gained popularity. They are more easily cold workable than alpha-beta alloys, heat treatable to high strengths, and some have better corrosion resistance than commercially pure grades.

Alpha and Beta Alloys

These are typically medium to high-strength materials with tensile strengths ranging from 620 to 1250 MPa and creep resistance ranging from 350 to 400°C. In addition to tensile properties, they also have low and high cycle fatigue and fracture toughness characteristics.

As a result, people developed thermomechanical and heat treatment procedures to ensure that the alloys provide an optimal balance of mechanical properties for various applications.