Titanium, its alloys and 3D printing with Ti6Al4V

Titanium and its alloys, particularly Ti6Al4V, are of great importance in 3D printing. Titanium is a metal found in nature as an oxide, specifically rutile (TiO2) or ilmenite (FeTiO3). The extraction of pure titanium is carried out using the Kroll Method. In its basic and simplified form this consists of obtaining titanium tetrachloride (TiCl4) by chlorination at 1000ºC in the presence of carbon oxide, which is subsequently reduced with magnesium or ground sodium in an inert atmosphere at a temperature of between 800-850ºC, obtaining pure titanium. The high reactivity of titanium makes it difficult to obtain it as pure metal, so a sample with 99.9% purity is commercially classified as pure titanium. Because of this, the material is generally used in combination with other elements to form an alloy.

The main properties of titanium are its high mechanical strength, low density and excellent corrosion resistance. This makes titanium and its alloys attractive materials for several sectors including aeronautics, aerospace, and medicine among others. The only significant disadvantage of titanium is its high price. Additionally, due to the properties of its alloys, the materials have vast potential for the manufacture of parts and elements by additive manufacturing.

Bugatti additively manufactured a titanium brake. | Credits: Bugatti

Classification and types of titanium alloys

Titanium alloys are divided into three groups: α, α + β and β, depending on the phase or phases present in the microstructure of the alloy. At this point, many of you may be wondering what a microstructure and phase is. The microstructure is the structure of a material that is visible under an optical or electron microscope. It provides information about the size, shape and orientation of the individual crystals or grains that make up a material. The microstructure also largely defines the properties of the material. In contrast, a phase is a region of the material with homogeneous physical and chemical properties. As such, it differs in its microstructure and/or composition from another region. Both characteristics of the material depend on the rate at which it cools from a liquid to solid state as well as the heat treatment applied.