The best materials are, by and large, the most expensive: carbon fibre, diamond and scandium all have properties to lust for, but an eye-watering price tag to match. Now, material scientists have tweaked an iron-aluminium alloy at the nano-scale to make a material that’s as strong and light as titanium, another expensive material, but just a tenth of the cost.
A team from Pohang University of Science and Technology, in South Korea have manipulated the structure of an iron-aluminium alloy to create a new kind of material that could find application in everything from bicycles to aeroplanes.
Steel is renowned for its strength and low price, but is very heavy. To make use of it in scenarios that demand light weight — without resorting to buying titanium — material scientists often alloy it with aluminium, which is light and also mercifully cheap. The mixture of aluminium and steel also usually includes a sprinkling of manganese to make it less brittle, but even then, the material is still usually too brittle for use in vehicles.
Now, the team from South Korea has added nickel to the mixture. The addition of this metal brings about a reaction with some of the contained aluminium, forming what are known as B2 crystals. Sitting both within the grains of steel in the alloy and at their boundaries too, the crystals — just a few nanometers in size — resist shear forces in the material. Because, ultimately, all materials fail by shear, where one layer of atoms slides across the other, taking microscopic cracks with it, increasing the resistance to shear forces increases the strength and stops the material failing by cracking.
Enough, in fact, to provide the new alloy with the same strength as titanium. The mix of steel and aluminium also provides a density similarly to that of the more expensive metal, too. The raw materials and (proposed) processing techniques also mean that the material could, when made at scale, cost just a tenth of what titanium does, too.
All of which is wonderful — but, so far, the metal has only been made in the lab. Now, The Economist reports, POSCO — which is one of the world’s largest steel companies — is starting trials to create the material at industrial scale. Those tests should begin this year. If they’re successful, we could soon be using it to make anything where titanium is currently desirable but prohibitively expensive. [Nature via The Economist]
Picture: Hansoo Kim