With stricter global environmental regulations and growing consumer demand for better vehicle performance, lightweighting has become an inevitable trend in the automotive industry. However, lightweight materials such as aluminum alloys, magnesium alloys, and carbon fiber composites come with very different physical properties and processing requirements compared to traditional steel. Consequently, conventional metal joining methods often prove inadequate for multi-material vehicle body manufacturing.
This challenge has accelerated the development of advanced joining technologies, which continue to evolve alongside new materials. To fully embrace the lightweighting movement in automotive manufacturing, it’s essential to first understand the key lightweight materials available today—and the unique properties that set them apart.
Currently, four main types of materials are driving automotive lightweighting: aluminum alloys, magnesium alloys, high-strength steel, and carbon fiber composites.
1. Aluminum Alloys – With a density of only about one-third that of steel (2.7 g/cm³), aluminum alloys offer high specific strength, excellent corrosion resistance, easy forming, and recyclability. They are widely used in non-structural or medium-load components such as hoods, fenders, battery trays, and chassis parts.
A prime example is Jaguar’s XFL, where aluminum alloys account for 75% of the body-in-white, making it 20–45% lighter than an equivalent steel structure. Similarly, NIO’s ES8 leverages Novelis’ advanced automotive aluminum alloys across its body, including the all-aluminum front and rear subframes, chassis, and suspension. Aluminum makes up an impressive 89% of the ES8’s body structure.
(Image from: NIO official website https://www.nio.cn/es8)
2. Magnesium Alloys – With a density of just 1.7 g/cm³, magnesium alloys are even lighter than aluminum alloys and offer excellent damping performance. They have already been successfully applied in components such as steering wheel frames, instrument panel frames, seat frames, trunk lid inner panels, and door impact beams.
Since magnesium prices fell below those of aluminum in 2024, magnesium alloys have become more cost-competitive, making their use in automotive parts increasingly attractive. Meanwhile, advances in corrosion resistance have enabled magnesium alloys to replace other materials in relatively exposed components such as electric drive housings.
For example, SAIC Motor has mass-produced magnesium alloy motor housings for its IM models, and in November 2024, it released its second-generation magnesium alloy housing. Manufactured using semi-solid die-casting technology, this new generation improves both material strength and corrosion resistance.
( Image from SAIC Motor’s official website: www.immotors.com/global/en/ls7_detail )
3. High-Strength Steel – Known for its high strength, low cost, and excellent cost-effectiveness, high-strength steel plays a critical role in enhancing vehicle body safety. It is commonly used in body frames, structural components, and connections between inner and outer panels. For instance, Scania’s NTG trucks utilize all-steel bodies, while General Motors’ GMC pickups feature steel–aluminum hybrid structures.
4. Carbon Fiber Composites – Offering exceptional lightweighting potential, carbon fiber composites are about 50% lighter than aluminum alloys while providing high stiffness and strength. They are already in use across a variety of structural parts, including hoods, fenders, roofs, trunks, and door panels. Notable applications include the BMW 7 Series, which incorporates carbon fiber reinforcements in the C-pillar area, and Tesla’s Model Y, which integrates a large die-cast body with carbon fiber–reinforced plastic for added strength and weight savings.
