By introducing perforations into the steel, we create a large number of edges, which interrupt the path of incoming projectiles
Peter Brown, MoD
For thousands of years, steel has been used to make or do just about whatever we ask of it, from ancient suits of armour to modern skyscrapers. It has been mass produced since the mid-19th century, and global production of this most ubiquitous of materials currently stands at more than 1.4 billion metric tonnes per year.
Although all steel consists primarily of iron and carbon, it has an almost infinite variety of properties, depending on the type or amount of other elements added to the mix, or the temperature at which the steel is produced. This complexity makes steel extremely versatile, but also very difficult to understand and to design from the atomic level.
Professor Harry Bhadeshia of the Department of Materials Science and Metallurgy has spent the past three decades researching the nature of steel to develop new alloys for a range of applications. One of these alloys, super bainite, has been licensed to Tata Steel and is currently being manufactured in the UK by the company for use as super-strong armour for military vehicles, as well as for other applications.
Bainite is a microstructure that forms when austenite, a high-temperature phase of steel, is cooled to temperatures between 250 and 500°C. The structure of austenite transforms as it cools, when slender crystals of iron incorporate themselves into the structure, and carbon compounds known as carbides form. The resulting bainite structure is very hard, but the carbides make it brittle and prone to cracking.
Working in collaboration with Professor Peter Brown of the Ministry of Defence (MoD), Bhadeshia and Dr Francisca Caballero in the Department of Materials Science and Metallurgy set out to refine and enhance the properties of bainite, originally for use in gun barrels.
Image: Perforations in super bainite make the material even better at protecting armoured vehicles from projectiles
Credit: Tata Steel
Reproduced courtesy of the University of Cambridge