Hydro Magnesium Energized by New Alloys, Applications

DETROIT - BMW AG isn't the first high-volume auto maker to spec lightweight magnesium for a new engine block, but it is the first in a number of decades.

The new magnesium block debuted on some versions of the 6-Series sold in Europe last year and will be used for BMW's all-new, high-volume 3-Series launching this year.

This high-profile application, along with several others including the new Mercedes-Benz 7-speed automatic transmission case and the engine cradle for the new Chevrolet Corvette Z06, have officials at magnesium supplier Hydro Magnesium talking optimistically about the future here at the 2005 SAE World Congress.

The new BMW engine block, which features aluminum cylinder liners, is about 25% lighter than a comparable all-aluminum engine block.

That has other auto makers, including Audi AG, taking a serious look at magnesium for structural engine components, says Dugald S. Reid, director- North America sales and marketing, for Hydro Magnesium's Norsk Hydro Canada Inc.

Magnesium is a strong, highly formable metal that is substantially lighter than aluminum. It has been used sporadically by auto makers in a wide variety of applications since the 1950s and 1960s, from door frames and large instrument-panel components to the engine block of the original Volkswagen Beetle, Reid says.

However, industry sources say that despite its light weight, high cost and concerns about its strength when the metal is subjected to high temperatures over extended periods - known as creep strength - have limited magnesium's role in cars and trucks.

The average amount of the material used per vehicle in the U.S. has grown from about 3 lbs. (1.4 kg) per car in the 1970s to a modest 10 lbs. (4.5 kg) today.

However a new series of heat-resistant magnesium alloys, known as AE alloys, should enable magnesium to win more applications in future cars and trucks, Reid says.

The new BMW engine block was in development prior to the introduction of the alloys, but the improved properties definitely played a role in General Motors Corp. specifying magnesium for the 22-lb. (10-kg) engine cradle of the Corvette Z06, in part because its location puts it very close to at least one of the 505-hp engine's catalytic converters, Reid says.

Hydro Magnesium officials say they expect more engine cradles to be designed with magnesium in mind in the near future.

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