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IALS, MULTIPLE WAYS by Gary S. Vasilash > "I don't think one material is the solution for lighter-weight vehicles," says Swamy Kotagiri, executive vice president of engineering and research and development at Magna (magna.com). Kotagiri, along with many of his peers in the industry, are taking a broader view of material solutions to meet fast approaching fuel economy regulations. "We are focused on multi-material solutions," he says. "For example, if we're making a column, maybe we want a steel enclosed section in one area but need an aluminum casting in another because it is an intricate shape. Now the challenge is how do we put these two materials together?" Conventional fusion welding, where joints are formed when molten metal cools, doesn't work very well when joining dissimilar metals like, aluminum and steel, so manufacturers are beginning to use solid-state welding techniques that require only pressure and friction to form robust bonds. q Honda uses friction stir welding to join aluminum and steel components in the subframe of the 2013 Honda Accord. p Dana uses magnetic pulse welding to join steel and aluminum in its drive shafts. "There's very little opportunity for fusion welding mixed materials," says Matt Zaluzec, manager of materials and manufacturing research at Ford. "We're looking at solid-state welding processes that are scalable." While many of these processes have been used for low-production or even just lab work, it is necessary to achieve higher volume capability for them to become viable for use at places like Ford. Here's a rundown of a few of the welding methods Zaluzec, Kotagiri and others in the industry are exploring: Friction stir welding (FSW): FSW was developed in the early 1990s at The Welding Institute in Cambridge, England, and has been used by NASA for space shuttle parts, Apple to bond the aluminum bodies of iMac computers, and Honda to join aluminum and steel in the 2013 Accord front subframe. FSW involves a rotating tool pressing into the intersection of the two metals to be joined so that the friction heats the surrounding material to a plasticized state around the probe. As the tool rotates it stirs the materials so that a mechanical bond is formed. No melting occurs, leaving the weld in the same condition as the parent material(s). This process has fewer elements to control than arc welding (e.g., purge gas, voltage and amperage, wire feed, travel speed, shield gas, and arc gap all must be regulated. For FSW, there are only three parameters to control: rotation speed, travel speed, and pressure. What's more, there is an energy-saving beneft. For the Accord subframe, Honda claims the FSW process uses 50% less electricity compared to conventional welding. Friction bit joining (FBJ): FBJ involves cutting and friction to form a bond. Last year, researchers at Brigham Young University's Friction Stir Research Laboratory (fsrl.byu.edu), working with the University of Ulsan in Korea and Korean automotive suppliers, joined a lightweight aluminum hub with a cast iron brake rotor by inserting a thin layer of steel between the two metals. Michael Miles, a manufacturing engineering technology professor at BYU and co-developer of the process, explains how it works when joining aluminum to steel: "The bit rotates at a high speed"—around 2,500 rpm—"and cuts through the top layer of material, which in this case is an aluminum sheet." When the consumable steel bit encounters the steel, via heat and 31