General Motors is testing what it claims is an industry-first thermal-forming process and proprietary corrosion resistance treatment for lightweight magnesium sheet metal. Magnesium weighs 33% less than aluminium, 60% less than titanium, and 75% less than steel. The new technology will allow greater use of the high-strength alternative to steel and aluminium.
While die-cast magnesium has been used in a range of parts, including steering wheels and engine cradles, GM claims to be the first to use thermal-formed magnesium sheet metal in structural applications, and it expects magnesium sheet applications to grow with additional materials and process improvements targeted at reducing cost.
Although offering a significant weight savings, magnesium has proved problematic in terms of corrosion resistance and reliable strength using traditional panel forming methods. GM has patented a process that heats the magnesium to 450 degrees Celsius (842 degrees Fahrenheit), allowing the material to be moulded into precise, rigid shapes.
Using this process, GM developed a production-ready magnesium rear deck lid inner panel. The part survived testing – 77,000 robotic slams and 250-kilogram impact drops – without any issues. On the production ready rear deck lid inner panel, GM can remove 1 kilogram (2.2 pounds) of weight compared to an aluminium deck lid inner panel. In terms of corrosion, GM says its treatment for thermal-formed magnesium resisted 10 consecutive weeks of 24-hour environmental tests involving salt spray, 100% humidity and extreme temperatures.
“This innovative use of magnesium is just one example of how GM is leveraging breakthrough technologies that will benefit our customers around the globe,” said Jon Lauckner, GM Chief Technology Officer and Vice President of Global Research & Development. “Using high-strength lightweight materials such as magnesium and aluminium is one of the most effective ways to improve vehicle fuel economy and driving performance.”
According to estimates from the United States Automotive Materials Partnership, by 2020, 350 pounds of magnesium will replace 500 pounds of steel and 130 pounds of aluminium per vehicle for a 15% reduction in weight. Such a weight loss could lead to a fuel savings of 9-12%.
“Every gram of weight reduction matters when it comes to improving fuel economy,” said Greg Warden, GM Executive Director for global vehicle body engineering. “Being able to replace heavier metals with one of the lightest will help us deliver better fuel economy to customers around the world while also still providing the safety and durability they expect.”
Overall, GM is looking to expand the use of low-mass parts on its global vehicle line-up. In terms of the new magnesium technology, it plans to pursue licensing opportunities to allow component suppliers to produce the magnesium inner panels.
According to Automotive News, the OEM plans to conduct a production run of 50 vehicles to be bought by consumers in the fourth quarter. It was not indicated which model(s) would be used for the test of expanded magnesium use.
Meanwhile, GM is also pursuing new developments in aluminium welding technology, which it believes will allow for greater use of aluminium on vehicles.
