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Because a 10% reduction in vehicle weight can result in a 6%-8% fuel economy improvement, lightweight materials like aluminum are essential for improving vehicle efficiency.  In an EERE Vehicle Technologies Office-supported project, researchers have demonstrated a new process that will enable manufacturers to expand the use of lightweight aluminum in cars and trucks.

A partnership with General Motors, TWB Company LLC, Aloca, and Pacific Northwest National Laboratory (PNNL) developed a friction stir welding process that reduces production time and costs while yielding strong and lightweight parts.  Using aluminum, it can deliver a car door inner panel that is 62 percent lighter and 25 percent cheaper than that produced with today’s manufacturing methods while maintaining the speed, scale, quality and consistency required by the auto industry.  This technology is so promising that a major supplier has invested in new equipment to manufacture aluminum components using this process.

The friction stir welding process builds on a common technology known as “tailor welded blanks (TWBs).” Usually used with steel, TWBs reduce weight in vehicles by using heavy thicker sheet metal only where it is needed.  For example, a door may require having thick sheet near the door hinge for strength, but can use thin sheet everywhere else.  TWBs connect together the thin and thick sheet that is then cut into an appropriate size and shape.

Before this process, vehicle manufacturers had no commercially viable way to produce aluminum TWBs.  While manufacturers typically produce steel TWBs with laser welding, this process has proven more challenging with aluminum because molten aluminum is very reactive when exposed to air.  Similarly, friction stir welding, which uses a specialized rotating tool to weld metal together below the melting temperature, also previously existed as a technique.  However, it was too slow for commercial use and did not produce components with consistent surface characteristics.

The research team decided that improving friction stir welding to allow companies to manufacture aluminum TWBs had very good potential for expanding the use of aluminum in vehicles.  Over three years, the team combined a variety of expertise to develop new tooling, processes, and models that resulted in a friction stir welding technique ten times faster than current ones.  With this new process, a single friction stir welding machine can join more than 250,000 automotive components a year. 

Using this technology, the TWB Company independently welded, formed and analyzed more than 100 aluminum blanks in close coordination with GM. Having proven its potential, GM stamped its first full-sized, aluminum inner door panel using TWB technology that met GM’s high standards. Since then, the TWB Company has become the first in the world to install and operate equipment for aluminum TWBs that can manufacture them in high-volume production quantities. 

The Vehicle Technologies Office (VTO) develops and deploys efficient and environmentally friendly highway transportation technologies that will enable America to use less petroleum. These technologies will provide Americans with greater freedom of mobility and energy security, while lowering costs and reducing impacts on the environment.

The Office of Energy Efficiency and Renewable Energy (EERE) success stories highlight the positive impact of its work with businesses, industry partners, universities, research labs, and other entities.