Innovations for Lightweighting: FCA slashes Pacifica mass with magnesium, hot-stamped steel

May 1, 2017

Lindsay Brooke

Hot-stamping grades of high-strength ArcelorMittal steel help make the 2017 Pacifica lighter and safer. FCA also opted for magnesium and aluminum to reduce mass.

For the past 20 years, the steel industry has parried the most aggressive thrusts of its aluminum competitors and outpaced them in real-world vehicle mass reduction at moderate cost. Steel’s success comes from continuous development of new alloys in combination with a commitment to process R&D, according to materials experts.

FCA engineers partnered with ArcelorMittal Steel in 2012 when the automaker kicked off the 2017 Chrysler Pacifica program. The development consumed 2,000 engineering hours and went through approximately 300 design iterations. The partners identified the side structure of the vehicle’s body-in-white, specifically the door ring and B-pillar, as the area of most opportunity for weight reduction and improved safety performance, according to Pacifica Chief Engineer Jessica LaFond. It is the world’s first five-piece hot-stamped laser-welded door ring and B-pillar combination, she told Automotive Engineering.

Using its patented laser ablation process, the steelmaker combined two HSS grades — Usibor, a hot-stamping grade that supports weight reduction in advanced shapes that require higher tensile strength, and Ductibor, an energy-absorbing grade designed specifically to complement Usibor in hot-stamping applications and offer ductility — to help manage the energies in small-offset and side-impact crashes.

The one-two punch of steel grades is part of a body design strategy incorporating a magnesium cross-car beam and magnesium liftgate inner casting, the latter a collaboration between FCA and Meridian Lightweight Technologies. The Mg casting is part of a four-piece assembly with aluminum-sheet upper and lower outer panels and a stamped-aluminum wiper reinforcement. The new lightweight liftgate is a 50% (22 lb/10 g) mass reduction from that of the outgoing Chrysler minivan. Magnesium’s ductility helps the vehicle meet crash requirements and the casting contributed to a significant bill-of-material reduction, LaFond noted.

Combined with a move to aluminum sheet for the large sliding doors (saving 40 lb/18 kg), the re-engineered BIW contributed to about half of the 250 lb (113 kg) total weight reduction for the Pacifica compared with the previous vehicle. At 4,316 lb (1,958 kg) base curb weight, it is the lightest minivan available and helped contribute to the vehicle’s nimble handling — a factor in Pacifica being voted 2017 North American Utility of the Year. It’s also the first minivan to achieve an IIHS 2017 Top Safety Pick Plus.