Tech Briefs
Light metal gains acceptance

Magnesium is close to moving from a vehicle interior-application choice to being used in engine-components and exterior body- panels.

"The automotive industry has crossed the threshold from using magnesium in a protected environment — predominantly interior applications — to an unprotected environment," said Materials Engineer Kerry Border during a break at the 11th annual Magnesium in Automotive Seminar, sponsored by the International Magnesium Association, in Dearborn, MI. "In the future, magnesium components must withstand the environment — rain, road salt, dirt — and that's a big step."

Production magnesium components currently emphasize interior applications, such as steering column brackets, instrument panel, seat frames, steering wheel, ashtray door, sunroof track assembly, and mounting structure for compact disc player/cassette player. But future applications expand magnesium's territory to roof panels, hood, rear deck lid, wheels, intake manifold, cylinder head cover, oil pan, starter/alternator, and engine block.

"Six different European car manufacturers are developing and evaluating a magnesium engine block," said Jo M.A. Willekens, Director - Market Development for Hydro Magnesium Marketing GmbH in Europe. "One car manufacturer has a magnesium engine block in the road test phase. The first production magnesium engine block is expected in three to five years."

Chemists continue to work on developing an appropriate coolant composition for the magnesium engine blocks. "Specialized chemical companies are working to solve this issue," said Willekens. "Hydro Magnesium Market Development Europe is not developing (these) engine blocks, but the company contributes on technical issues."

High-temperature areas under the hood — such as automatic transmission cases and engine components — are growing as a magnesium focal point. "Alloy development activities in the 1990s show that it's possible to develop magnesium alloys with good creep resistance," said Mihriban Pekguleryuz, Senior Scientist for Noranda Inc. Technology Centre in Quebec, Canada. Noranda recently developed three die-cast (cold chamber) magnesium alloys, and further evaluations for high-temperature strength and creep resistance continue. Developing a magnesium alloy with good creep resistance is vital for engine-compartment applications. "Good creep resistance for an automatic transmission case would mean the material would not deform and the bolts would not loosen," Pekguleryuz said.

The trend toward magnesium as a material choice has been gradual. In 1990, a typical vehicle sported just 1.4 kg (3 lb) of magnesium. Ten years later, a typical vehicle has about 3.6 kg (8 lb) of magnesium — still far short of the nearest light metal competitor, aluminum, which is estimated to claim 112 kg (246 lb) per vehicle in 2000. But the materials scorecard will change. Ford Motor Co. is giving magnesium more than a passing glance. "The current 20,000 t (22,045 ton) of magnesium is the highest ever for Ford Motor Co., but that's partly due to more vehicles (and acquisitions)," said Tom Sweder, Manager, Weight/CAE Technology Engineering at Ford's Product Development Center in Dearborn, MI.

A projection of 40,000 to 50,000 t (44,100 to 55,115 ton) in the 2004/05 timeframe includes body structures as well as instrument panel structures. As an example, the 2001 Ford Explorer sport utility vehicle will have a magnesium instrument panel structure, which will eventually reach the entire F-Series line. One stumbling block to widespread automotive magnesium usage has been cost.

"Strictly in terms of material cost, all lightweight materials have a disadvantage when compared to steel," said Alan Luo, Senior Research Engineer Materials & Processes Lab at the General Motors Research & Development Center in Warren, MI. "But does that mean it would prevent us from going to magnesium? No." Methods to offset cost, according to Luo, include parts consolidation as well as more efficient design and manufacturing initiatives. He believes using magnesium in future powertrain applications — engine block, manual and automatic transmission case, oil pan, intake manifold, and water pump housing — as well as chassis applications will happen once certain practical issues are solved. "For instance, processes to produce porosity-free magnesium castings are needed for chassis applications."

GM says there is much to like about magnesium as it relates to business. "It's strategically important for future growth," Luo said.

Magnesium is now the center of attention for the United States Council Automotive Research's (USCAR) automotive material team. USCAR initiatives investigate ways to develop a family car that can attain 2.9 L/100 km (80 mpg). April signaled the start of a four-year structural cast magnesium project that aims to resolve the issues blocking widespread magnesium usage. "The current light-metal team is experienced and ready to transition into magnesium," said Richard Osborne, Staff Development Engineer/Cast Materials Processing for GM.

The $10 million project involves the U. S. government, automakers, suppliers, universities, and national laboratories. "We have a number of dragons to slay," Osborne said, citing things like material shrinkage, corrosion, analysis techniques, and joining methods.

Magnesium is going to make its presence known. "From the projects I know of at this moment in Europe, I predict 50 to 60 kg (110 to 132 lb) magnesium by weight per vehicle in 10 years," said Hydro Magnesium's Willekens.

Kami Buchholz