The lightweight debate

As automakers focus more on light-weighting vehicles, some debate remains over which is better: alloys such as aluminum and magnesium or advanced high-strength steels.

Some firms are even dabbling in composite plastic materials in anticipation for the still unknown future of the electric car.

Aluminum and magnesium are used for component parts, but industry professionals argue the cost of these materials is high and unpredictable, and making the switch from conventional steel products is far too pricey.

For an industry ruled by high volume, low-value parts, cost is king.

“Aluminum is becoming an important component part for engine blocks and body parts,” says Steve Treiber, engineering professor at McMaster University in Hamilton, Ont. “And the only time you’re going to find magnesium is in wheels and engine components. But both are strictly for high-end applications.”

“These are light, high-strength components that you would need in a car intended for racing. You’re not going to see them in a Honda Civic unless some kid decided to tune his car,” he adds.

Indeed, light-weight materials such as aluminum, magnesium and titanium are mainly used in high-performance race cars that reach 12,000 RPM, or in luxury niche vehicles.

Some automakers such as Aston Martin are going even more high-end.

Aston Martin unveiled its One-77 two-door sports coupe, which featured a complete carbon fibre chassis at the 2009 Geneva Motor show. The layers of the carbon fibre are applied by hand and put into an autoclave multiple times for heating and forming. And its sleek exterior body panels are made of handcrafted aluminum.

“It’s a $2-million car,” laughs Treiber, “so it’s a little out of most people’s price range.”

Although the tensile strength and crashability of these alternatives are comparable to steel, they probably won’t make it into mainstream production unless the cost comes down and a cheaper process is developed

Eugene Ng, a mechanical engineer at McMaster University, partnered with Treiber to create the Manufacturing Technology Network to promote innovation, technology and collaboration in manufacturing. Through this network they’ve worked with many in the auto industry on research and development projects.

According to Ng, there’s not a lot of magnesium and aluminum development being done in Canada because the Big Three dictate what materials parts manufacturers will use.

With new generations of advanced high-strength steel hitting the market, the steel industry still has a firm grip on the auto sector.

Gunter Riegel, one of the owners of Markham-based Woodbine Tool and Die Manufacturing Ltd. (WTD)—a Tier Two tool and die manufacturer that produces stampings and welded assemblies for the automotive industry employing 300 people—admits he looked into working with magnesium but passed on it, partly because of cost fluctuation.

“I’m not equipped to work with magnesium here and I don’t really want to because it’s a dirty operation,” says Riegel. “Depending on what kind of machining you do, it can be somewhat dangerous.”

Treiber concurs, “When machining magnesium, the mixture of heat, pressure and oxygen can make it combust. But if you’re forming it, it’s okay.”

Riegel maintains steel is still one of the most cost effective and stable commodities.

The first generation of advanced high-strength steel (AHSS) that came out in the late 1990s was dual-phase with a “transformation induced plasticity” (TRIP)—a microstructure comprised of austenite embedded in a matrix of ferrite.

For the second generation, an extreme alloy chemistry was introduced consisting of about 20 per cent manganese.

But Peter Bradgley, director of research for US Steel Canada said this generation had drawbacks because it was too complex to manufacture and accordingly more expensive.

“Steel makers are now focused on developing a third generation of AHSS. This new alloy concept will have a cost structure [similar to] the first generation,” says Bradgley.

As the strength of the steel goes up, the ductility is reduced. But using less manganese, steel makers are developing this new generation to maintain high strength, as well as ductility.

With the new generation of AHSS, automakers will be able to reduce the gauge of the steel. 

But as the industry moves closer to producing electric vehicles (EV), both Treiber and Ng believe that making them light enough won’t be achieved by any single metal currently in use. It’s going to end up being some composite material.

Ng and Treiber agree some steel engine components will still be needed, but 10 years from now the $20,000 cars will be plainer with less luxurious components.

If light-weighting is the key to moving the industry into the electric era, the OEMs need to rethink vehicle materials and how they are going to convince consumers they can do with fewer bells and whistles.