A Key Material for Automotive Lightweighting: The Advantages, Challenges, and Future of Magnesium Alloys [SMM Analysis]

1 Magnesium Alloys Drive Automotive Industry Transformation with Lightweighting Advantages

With the rapid advancement of the automotive industry, energy security and energy conservation & emissions reduction have become core issues driving the sector's sustainable development. Automotive lightweighting, as a critical path to enhancing vehicle performance and creating value for users, is playing an irreplaceable and vital role. The main approaches to achieving automotive lightweighting include:

1. Structural optimization, such as adopting integrated design;

2. Application of advanced materials, like aluminum alloys and magnesium alloys;

3. Introduction of advanced manufacturing processes, such as friction stir welding and laser welding technology;

4. Integration of new technologies, such as lithium battery start-stop systems.

Materials form the foundation of lightweighting. By selecting materials with low density, high static strength, high elastic modulus, and excellent fatigue strength, the lightweighting process can be advanced at different levels. Therefore, magnesium alloy, as an advanced lightweight material, is gradually becoming an important choice in automotive lightweighting.

2 Status of Magnesium Usage in the Automotive Industry
2.1 Technology Development Trends
The 'Technology Roadmap for Energy-Saving and New Energy Vehicles 2.0' clearly states that China will vigorously promote the application of magnesium alloy materials in the automotive field and has set clear targets for magnesium usage per vehicle: reaching 15kg by 2020, 25kg by 2025, and increasing to 45kg by 2030.

However, despite continuous technological developments in magnesium alloys, their practical application scale and effectiveness still fall below expectations.

As of now, the highest average usage of magnesium alloy per vehicle in China is approximately 19 kg, achieved by Seres (SaiLisi) Motors. Currently, Baowu Magnesium has cooperated with Seres to jointly promote the application of magnesium alloys in automotive lightweighting. Both parties will leverage the R&D capabilities of Boao Magnesium & Aluminum to accelerate the promotion and application of magnesium alloy components in mass-produced models, supporting the technological upgrade of lightweighting in new energy vehicles.

Meanwhile, the commercial vehicle sector is also progressively advancing the pilot application of magnesium alloys. The second batch of magnesium alloy lightweight trailers jointly developed by Xi’an Jiaotong University and Shaanxi Automobile Group accumulated over 30,000 kilometers during more than three months of trial operation. With excellent performance and stable operation, they fully demonstrated the application potential of magnesium alloy materials. These trailers adopt a lightweight design for the box body and aluminum alloy frame, achieving a weight reduction of 800 kg in the first phase of development, with magnesium alloy consumption per vehicle reaching 800 kg.

Overall, magnesium alloy technology is developing rapidly, but large-scale application still requires more test verification and coordinated promotion from various factors. Looking at the downstream consumption structure, the transportation sector already accounts for 60% of magnesium alloy consumption and will become the most important growth direction for magnesium alloys in the future.

2.2 Usage Status and Future Outlook
In terms of average usage, large magnesium alloy castings are currently mainly considered in new energy passenger vehicles priced above RMB 100,000. For example, NIO and XPeng Motors use magnesium alloy Cross Car Beams (CCB) in almost all their models, with a usage of about 5 kg; BYD applies them only in some high-end models, while Chery Motors is in the R&D and initial promotion stage.

Comprehensive industry analysis estimates that by 2025, the average magnesium usage per new energy passenger vehicle priced below RMB 200,000 will reach 4.4 kg, while models priced above RMB 200,000 are expected to reach 12.35 kg. In comparison, the average magnesium usage per fuel-powered vehicle is relatively low, at about 1.46 kg. The overall penetration rate of magnesium usage in automobiles is projected to be around 30%, maintaining a rapid upward trend. Based on the current development pace, by 2030, the penetration rate of magnesium usage in automobiles is expected to reach 85%, achieving multiplicative growth.

2.3 Main Application Components and Technical Characteristics
Currently, the application range of magnesium alloy components in the automotive field is continuously expanding, mainly divided into four categories: interior, body, chassis, and transmission. Typical interior applications include seat frames, instrument panel (IP) frames, center console brackets, and LCD display backplanes; power system applications include E-drive housings, engine covers, transmission cases, and oil pans; chassis system applications include wheels, steering wheels, and subframes.

The following are the main product applications and their technical characteristics:

CCB (Cross Car Beam)
Widely used by multiple OEMs globally, with various design strategies based on different performance and integration requirements. This component adopts a lightweight integrated structure, replacing traditional steel welded parts, significantly reducing weight while meeting multi-functional installation requirements. Its weight typically ranges from 3.6-4.8 kg, achieving a weight reduction of about 3 kg compared to traditional CCBs.

Seat Frame
Magnesium alloy seat frames offer good NVH performance and lightweight advantages, with high integration and excellent stiffness/strength, meeting requirements for常规使用 (conventional use) and extreme crash conditions. Currently, the backrest and seat pan frames for front, second, and third-row seats have achieved mature application. Among them, the backrest frame weighs about 1.4-1.8 kg, the seat pan frame about 1.3-2.8 kg, and the rear seat bracket about 3.5-5 kg. Overall, it can achieve a weight reduction of about 20 kg.

Inner Door Panel
Liftgates and swing doors have achieved mass production in North America and are applied in multiple mainstream OEM models globally. The magnesium alloy integrated tailgate inner panel uses large-scale die-casting technology, integrating multiple components such as hinge reinforcement plates, inner panel reinforcement plates, lock reinforcement plates, and strut reinforcement plates. Meridian introduced advanced thermal balance technology domestically for the first time, using a 4200-ton die-casting unit to develop the world's largest automotive magnesium alloy tailgate inner panel, measuring 1.4m high, 1.7m wide, and 0.26m deep. Through a variable-thickness integrated structural design, it eliminates the original reinforcement plates and metal inserts, integrates 54 parts, achieves a 21.3% weight reduction compared to plastic tailgates, and weighs approximately 5-7 kg.

E-drive Housing
The transfer case housing is a mature product whose acoustic and vibration performance is superior to aluminum components. The average weight is customized based on the vehicle model, achieving an overall weight reduction of about 8 kg. Since the beginning of this year, nearly ten magnesium alloy E-drive housing projects have entered mass production, with a usage per vehicle reaching 15-30 kg.

3 Application Advantages of Magnesium Alloys
3.1 Significant Price Advantage
Global primary magnesium prices have long remained within a reasonable fluctuation range compared to aluminum prices. Rough estimates show that substituting magnesium for aluminum can achieve direct cost reduction of about RMB 12 per kg. Furthermore, magnesium alloy molds have long life and low cost, good fluidity and high die-casting efficiency, are easy to cut with superior CNC machining efficiency, resulting in comprehensive costs being about 15% lower than aluminum alloy.
Data from January to August 2023 shows that the average price of magnesium alloy was RMB 2230/ton lower than aluminum alloy, and the Mg/Al ratio (magnesium ingot/aluminum ingot) averaged 0.83.

3.2 Strategic Advantage of China's Magnesium Resources
Magnesium is one of the most abundant elements in the earth's crust, accounting for about 2.77%. China's magnesium ore reserves account for over 70% of the global total, including more than 4 billion tons of magnesite-dolomite resources, and magnesium salt resources in western salt lake brines reaching 6.003 billion tons. Magnesium alloy is the only metal material that China can be 100% self-sufficient in, and it is also an important national strategic advantage resource.

3.3 Dual Advantages in Performance and Process
Magnesium alloy density is 1.8 g/cm³, 30% lighter than aluminum; specific strength reaches 191 σb/ρ, higher than aluminum; specific stiffness is close to aluminum alloy. It also possesses excellent noise reduction, damping, and electromagnetic shielding properties. In terms of process, magnesium alloy has good fluidity, suitable for thin-walled complex structural parts; low cutting resistance and good machinability significantly save tool wear. With continuous progress in material technology, magnesium alloys are constantly breaking through in properties such as corrosion resistance and high-temperature creep resistance, showing more comprehensive advantages compared to aluminum alloys, steel, and plastics, exhibiting huge potential for automotive lightweighting applications.

3.4 Continuous Upgrade of Die-casting Processes
Advanced processes such as semi-solid thixomolding are gradually being promoted in magnesium alloy die-casting. This process involves intense stirring to shear the primary dendrites, forming a spherical grain structure, significantly reducing slurry viscosity and improving fluidity. It offers advantages such as high precision, good quality, few defects, and low energy consumption, providing strong support for the wide application of magnesium alloy die-cast parts.

4 Limitations and Challenges in Magnesium Alloy Development
4.1 Flammable and Explosive Risks in Production Require Extra Protection
Magnesium alloys are prone to combustion and even explosion during melting and processing, posing high requirements for production safety. Therefore, more stable casting processes and highly flame-resistant magnesium alloys must be developed to improve intrinsic safety.

4.2 Chemically Active, Poor Corrosion Resistance
Magnesium alloys are highly susceptible to electrochemical corrosion and are highly dependent on the usage environment and surface treatment. Currently, low-cost protection methods (such as using aluminum fasteners) can mitigate local corrosion, but more economical and efficient corrosion-resistant technologies still need to be developed.

4.3 High Recycling Costs, Low-Carbon Production Still Faces Challenges
The recycling process for magnesium alloys is complex and energy-intensive, making truly low-carbon production difficult. Current methods mainly focus on improving recycling efficiency through in-plant recycling and die-casting machine-side recycling. Industry enterprises like Regal Magnesium are already promoting low-carbon magnesium production practices, but large-scale low-carbon pathways still require further breakthroughs.

4.4 Long Development Cycle, High Initial Technical Investment
The development of magnesium alloy components is not simple material substitution; it requires structural redesign and process adaptation based on their characteristics, leading to long R&D cycles and high initial costs. With the improvement of material databases, and the enhancement of prototyping and simulation capabilities, the application efficiency of magnesium alloys is expected to significantly increase, thereby promoting their large-scale application.

5 Conclusion

As the automotive industry continues to advance towards lightweighting and electrification, magnesium alloys are gradually becoming one of the key materials due to their significant lightweight characteristics, resource advantages, and continuously optimizing cost-effectiveness. Currently, although challenges remain in terms of corrosion resistance, production processes, and recycling, with the promotion of advanced processes like semi-solid die-casting, the improvement of material databases, and the deepening of joint corporate R&D, magnesium alloy application technology is constantly breaking through. In the future, driven by both policy support and industry collaboration, magnesium alloys are expected to achieve wider application in new energy vehicles, high-end models, and even commercial vehicles, providing solid support for energy saving, emissions reduction, and structural upgrades in the automotive industry.