Magnesium is the lightest construction metal, but also the most reactive. This means that it is very sensitive to corrosion, making it difficult to use in corrosive environments. For more than a hundred years, magnesium producers have strived to improve its corrosion characteristics by developing new, more corrosion-resistant alloys, and developing various coatings.
Mohsen Esmaily, a researcher in Atmospheric Corrosion at Chalmers University of Technology, Gothenburg, Sweden has changed the microstructure in magnesium alloys to make them more resistant to corrosion. This could encourage the transport sector to use these materials to decrease the weight of vehicles.
“In cars where every kilo of reduced weight is important, a transition to magnesium, which is 30% lighter than aluminium, the most common lightweight metal today, would mean a great step forward to reduce fuel consumption,” says Esmaily.
As the automotive industry comes under increasing pressure to raise energy efficiency and lower CO2, materials used in vehicle construction are coming under closer scrutiny. A recent version of the Range Rover Sport makes extensive use of aluminium and lightweight technology in general. The aluminium body is around 350 kg lighter than on the preceding model; the lighter body has a direct benefit in terms of allowing the reduced weight of other parts, e.g. lighter suspension and braking components. Together with the body, these reduce the weight of the vehicle by 420 kg. One of the many specific components that has been subject to a major reduction in weight is the rear sub-frame, made by Martinrea Honsel. This part is 15 kg lighter than its steel predecessor
By studying magnesium casts produced through a method called rheocasting, Esmaily discovered that the corrosion resistance of magnesium alloys produced this way was up to four times better than the same material when produced by conventional high pressure die casting.
Rheocasting of magnesium alloys was developed at Jönköping University in order to increase the strength of the material, but Esmaily’s research shows that the technique also gives the alloys the ability to withstand corrosion. Now that the connection has been mapped, new possibilities to optimise the microstructure for even better corrosion resistance have opened up.
“We will be able to create cast magnesium alloys that corrode much slower and that are stronger than ever before by controlling the microstructure of the alloy,” Esmaily says.
Great scientific discoveries in 2015 to change the world
Meanwhile Researchers from the University of California, Los Angeles, Henry Samueli School of Engineering and Applied Sciences have developed a super strong metal that is also very light. This new metal is made up of magnesium infused with a dense ceramic silicon carbide.
Magnesium infused with dense silicon carbide could be used for trains, airplanes, cars, mobile electronics and everything that uses metals. New magnesium based metal is super-strong yet light structural metal with extremely high specific strength. Lian-Yi Chen, who conducted the research said “The results we obtained so far are just scratching the surface of the hidden treasure for a new class of metals with revolutionary properties and functionalities.”
Australian and Chinese researchers have discovered a magnesium alloy that they say is the world’s strongest and lightest. Crucially, they say it doesn’t corrode. If it proves possible to use it in vehicle manufacturing, the researchers say cars could weigh hundreds of kilograms less, saving motorists up to 40 per cent on fuel.