Titanium in its pure form is a silvery metal known for its strength and low density compared to other similarly hard metals. In most industries, however, titanium alloy is much more commonly used.
Because of its physical and chemical properties, the metal has become useful in a wide variety of industries and applications such as medical equipment, chemical plants, military installations, and sports gear.
High strength, low density
Pure titanium is characterised for its specific strength, reaching up to 590 MPa tensile strength. In alloy form, this strength extends dramatically up to 1250 MPa (exhibited in Grade Ti-15Mo-5Zr-3AI alloy).
Its fatigue strength is about half of its tensile strength, and does not decline when exposed to welding or when submerged in seawater.
Titanium is a suitable component for applications that require a unique mixture of strength and material lightness.
- Density: 4.506 g/cm3
- Tensile strength: Minimum 200 MPa to beyond 1300 MPa (varies depending on purity and alloy composition )
Because pure titanium readily reacts with oxygen, it naturally produces an oxide film that gives itself protection against corrosive materials and environments. Its corrosion resistant against chlorine compounds, seawater, common acids, and extreme temperatures.
Titanium is also characterised by its refractory metal properties. Its melting point goes beyond 1650°C, significantly higher than aluminium and steel. Meanwhile, its coefficient of thermal expansion is 8.6 µm/(m·K), lower than steel and copper.
Applications of Titanium
Due to titanium alloy’s temperature and corrosion resistance, the material is used in the manufacturing of aircraft parts (airframe and fastening components), hydraulic system components, and landing gear.
The Lockheed SR-71 Blackbird military aircraft is made primarily of titanium, and was touted for its speed and design efficiency. Although the stealth spy plane was retired in the late ‘90s, aircraft manufacturers continue to incorporate titanium in modern aerial vehicles to increase strength while reducing weight.
Fig 1. The Lockheed SR-71 Blackbird military aircraft is primarily made of titanium.
Titanium has a high level of corrosion resistance against seawater, making it a suitable component for ship rigs, propeller blades and shafts, and other parts submerged in water.
The high strength-to-weight ratio of titanium lends itself to a range of applications in the sports industry. The material is used as components of sporting goods such as tennis rackets, baseball bats, golf clubs, bike frames, and ski equipment.
Due to its inertness and non-toxicity, titanium is used in a wide array of medical applications including surgical implants, dental implants, surgical tools, and accessibility equipment.
Powdered Titanium produces bright white sparks that are used in fireworks.
Titanium dioxide – the natural oxide form of the metal – has found its use as a whitening agent in paints, plastics, and toothpaste.
The biocompatibility, high strength-to-weight ratio, and corrosion-resistant properties of titanium is useful in the jewellery industry for bracelets, rings, and necklace chains.
Production and processing
Pure titanium readily reacts with oxygen, and so much of the titanium found in nature appears as ore or “sponge”, specifically rutile (TiO2) or ilmenite (FeTiO3). The Kroll process extracts TiO2 from the ore through a reduction process in the presence of chlorine gas, which produces titanium tetrachloride (TiCl4). Once purified via fractional distillation, TiCl4 is reduced by molten magnesium metal in a temperature-regulated vessel to produce pure titanium metal.
In the case of alloys, titanium is combined with aluminium, vanadium, tin, and/or palladium, among other metals. The variety of combinations creates a list of titanium grades umder alpha and beta categories. Each grade is designed for specific applications based on the resulting properties.
Heat treatment further intensifies the strength of titanium alloy, particularly in terms of fatigue resistance, creep stability, and integrity against fracture. The conditions for heat treatment largely depend on the alloy composition in order to optimise the physical properties of the material.