|Trunk lid inner panel is the first use of GM process for magnesium sheet metal. Click to enlarge.|
General Motors is testing an industry-first thermal-forming process and proprietary corrosion resistance treatment for lightweight magnesium sheet metal that will allow increased use of the high-strength alternative to steel and aluminum. Magnesium weighs 33% less than aluminum, 60% less than titanium, and 75% less than steel.
GM wants to expand its use of low-mass parts on vehicles around the world and will pursue licensing opportunities related to this novel technology. The goal is for suppliers to be able to use the process to provide significant amounts of magnesium sheet that will trim pounds from vehicle mass.
Using high-strength lightweight materials such as magnesium and aluminum is one of the most effective ways to improve vehicle fuel economy and driving performance.—on Lauckner, GM chief technology officer and vice president of Global Research & Development
GM R&D recently announced an industry-first welding technology for aluminum, which is expected to enable more use of the metal on future vehicles. (Earlier post.)
Until now, automakers have struggled to make reliably strong and non-corroding magnesium sheet metal panels using traditional panel forming methods. GM’s patented process turns increases the heat on magnesium to 450 °Celsius (842 °F), allowing the material to be molded into precise, rigid shapes.
Using this process, GM developed a production-ready magnesium rear deck lid inner panel that withstood 77,000 robotic slams and 250-kilogram impact drops without any issues.
Die-cast magnesium has been used in a variety of parts ranging from steering wheels to engine cradles, but GM is 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.
The United States Automotive Materials Partnership estimates that by 2020, 350 pounds of magnesium will replace 500 pounds of steel and 130 pounds of aluminum per vehicle, an overall weight reduction of 15%. This weight savings would lead to a fuel savings of 9% to 12%.
On the production ready rear deck lid inner panel, GM can remove 1 kilogram (2.2 pounds) of weight compared to a steel deck lid inner panel.
Every gram of weight reduction matters when it comes to improving fuel economy. 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.—Greg Warden, GM executive director for global vehicle body engineering
Automakers also have struggled to make magnesium corrosion resistant. GM’s proprietary treatment for thermal-formed magnesium resisted 10 consecutive weeks of 24-hour environmental tests involving salt spray, 100% humidity and extreme temperatures.