Magnesium is four times lighter than steel, making it a desirable metal candidate for wider application in manufacturing lightweight, fuel-efficient automobiles. Reducing vehicle weight by 100 kilograms can boost its energy efficiency by about 3.5 percent.
But pure magnesium is not easily malleable to make finished parts, so it requires mixing (alloying) with other elements
to boost its formability.
Now, scientists at the École polytechnique fédérale de Lausanne, Switzerland (EPFL), a research institute and university specializing in natural sciences and engineering, have developed models of magnesium alloys to understand how to make the metal more pliable. Their work will help predict how the world’s lightest metal behaves when mixed with different elements to determine which type of alloy provides the deformation capacity needed for a range of industrial applications.
The research was recently published in Science.
"Magnesium becomes much more malleable if you add a few atoms of rare-earth metals, calcium, or manganese," says William Curtin, a professor at EPFL's School of Engineering. "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."
Although it is ultra-low weight, magnesium has very low ductility. "That means it can break easily if it's deformed, and so it can't yet replace steel or aluminum," says Dr. Curtin. He says the solution is to find low-cost, readily-available minerals that can be used to create magnesium alloys. Rare-earth metals like yttrium and cerium are highly effective but otherwise do not meet these criteria.
"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. But exactly what affects an alloy's ductility remains a mystery and many materials are still developed experimentally.
In studying the interactions between magnesium atoms and the atoms of the elements added to make the alloys, the researchers found that certain atoms trigger a process that "cancels out" the mechanism that makes magnesium hard to shape. Magnesium's low ductility is due to its low number of moveable dislocations (linear defects that make metals flow plastically and make it less likely to break when it's deformed). The researchers found that adding certain elements increases substantially the number of moveable dislocations and enhances the metal's deformation capacity.
The alloys are still in the modelling stage, and the next step will be fabrication in the lab to see if they exhibit the right properties for industrial use and can be manufactured on a large scale.
Read more at https://phys.org/news/2018-01-lighter-vehicles-magnesium-alloys.html#jCp
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