New Alloys Could Lead to the Manufacture of Lighter Vehicles

Models of magnesium alloys have been developed by EPFL researchers in order to understand how to make the metal extra pliable. Magnesium is considered to be the lightest metal available on earth but cannot be shaped into usable forms in an effortless manner.

The researchers anticipate that the models will result in the discovery of new, more malleable alloys, thus enabling carmakers to make lighter vehicles capable of consuming less energy.

Shave just 100 kilograms from a car’s weight and it results in a boost in energy efficiency by almost 3.5%. Manufacturers in industries ranging from aerospace to automotive aim to develop lighter machines and equipment. Furthermore, the key could be magnesium – a metal that is four times lighter than steel and is also easy to find. The catch here is that pure magnesium is hard to stretch and form and thus cannot be used as-is. Hence, researchers at EPFL’s Laboratory for Multiscale Mechanics Modeling produced a model for predicting how the metal acts when mixed with varied elements in order to find out which type of alloy offers the deformation capacity required for industrial applications. Their research was featured in the Jan 26^th edition of Science.

Lighter, More Malleable Alloys

Magnesium becomes much more malleable if you add a few atoms of rare-earth metals, calcium, or manganese. We wanted to understand what’s going on in these alloys at an atomic level, so that we can identify which elements to add and in what amounts to make the metal pliable.

William Curtin, Professor at EPFL’s School of Engineering

Magnesium could be appreciated for its ultra-low weight, but it also contains extremely low ductility. “That means it can break easily if it’s deformed, and so it can’t yet replace steel or aluminum,” says Curtin. The solution is to discover readily-available, low-cost minerals that can be employed for creating magnesium alloys. Rare-earth metals like cerium and yttrium are greatly effective but otherwise do not fulfill these criteria.

The researchers previously identified the physical properties that make pure magnesium hard to shape. It is an established fact that adding certain elements can make it even more malleable. However, researchers do not have a good grasp of the physical mechanisms that take place – this means that they have a tough time predicting what the most excellent alloys would be. “Engineers often design and test new alloys of steel and aluminum, the most commonly used metals, to develop lighter, more solid or more malleable compounds,” says Curtin. However, the factors that affect an alloy’s ductility continue to be a mystery and a number of materials are still developed experimentally.

Studying Metals on an Atomic Scale

The interactions between magnesium atoms and the atoms of elements added to produce the alloys, were studied by the EPFL researchers. They discovered that specific atoms activate a process that “cancels out” the mechanism that causes magnesium to become hard to shape. The low ductility of magnesium is because of its low number of moveable dislocations, which are considered to be the linear defects that allow metals to flow plastically and that make it less likely to break when it is deformed. The researchers found that the addition of specific elements considerably increases the number of moveable dislocations, thus enhancing the metal’s deformation capacity. They then spent a number of months employing EPFL’s High-Performance Computing system in order to calculate, through quantum mechanics, the causes combinations of atoms to result in the highest ductility. “We were really lucky to have access to this equipment, which let us start working right away,” says Curtin.

From Modeling to Production

For now, the alloys still remain in the modeling stage. The next step will deal with fabrication in the lab in order to see if they have the correct properties for industrial use and also to study if they can be manufactured on a bigger scale.

"Mechanistic Origin and Prediction of Enhanced Ductility in Magnesium Alloys", Science, Zhaoxuan Wu, Rasool Ahmad, Binglun Yin, Stefanie Sandlöbes, W. A. Curtin