A review of magnesium die-castings for closure applications

1. Overview:

Title: A review of magnesium die-castings for closure applications
Author: J.P. Weiler
Year of Publication: 2019
Journal/Conference: Journal of Magnesium and Alloys
Keywords: Die-casting; Automotive applications; Closures; Lightweighting.

2. Background:

The Corporate Average Fuel Economy (CAFE) standards, enacted in 1975, mandated improvements in the average fuel economy of North American cars and light trucks. While initial increases were required from Model Year (MY) 1978–MY 1985, significant increases weren't seen until MY 2011.

Currently, rising fuel economy requirements are scheduled through MY 2025 and are primarily met through advancements in powertrain technology and vehicle lightweighting. Lightweighting can be achieved through various methods including computer-aided engineering (CAE) optimization of component or system designs, implementation of lightweight materials, and part consolidation.

This can lead to secondary or compounded lightweighting effects such as smaller engine blocks and transmissions, and reduced braking requirements. Magnesium die-castings in automotive applications typically utilize these three lightweighting methods. Their relatively low density, design flexibility, and fluidity enable significant part consolidation.

Historically, they've been used in instrument panel frames, seat frames, steering armatures, and transfer case applications. By 2015, the average North American vehicle contained approximately 5 kg of magnesium, a figure projected to triple by 2025.

This review examines recent research and, in some cases, production applications of magnesium die-castings in closure applications, as explored in various publications.

3. Research Objectives and Questions:

Research Objective: To review past and current developments of magnesium die-castings in closure applications and discuss the benefits and challenges of magnesium alloys for these applications, including casting design, corrosion and fastening strategies, and manufacturing design and assembly methodologies.
Key Research Questions: How can magnesium die-castings be applied to closure applications? What are the advantages and disadvantages of magnesium alloys for closure applications?
Research Hypothesis: Magnesium die-castings can contribute to weight reduction and part consolidation in closure applications.

4. Methodology:

Research Design: Literature Review
Data Collection Methods: Review of existing research papers and industry reports.
Analytical Methods: Qualitative Analysis
Scope and Population: Review of existing research and production examples of magnesium die-castings used in closure applications (e.g., automotive doors, liftgates).

5. Main Findings:

Magnesium die-castings have resulted in weight reductions of up to 50% and part count reductions in closure applications. The application of magnesium die-casting to the structural inner of the 2017 Chrysler Pacifica liftgate replaced nine parts from the previous generation, resulting in a nearly 50% reduction in liftgate assembly weight.

Other production examples include the 2004 Aston Martin DB9 magnesium side door inner (approximately 43% weight reduction), the 2010 Lincoln MKT magnesium rear liftgate inner (approximately 40% weight reduction), the 2009 Mercedes E-Class T-Model, the 2017 Aston Martin Vanquish S, the 2006 Mercedes CL-Class Coupe, and the all-new 2018 Jeep Wrangler's magnesium swing gate die-cast inner.

Lotus Engineering's study used over 26 kg of magnesium castings in a 2009 Toyota Venza, achieving a 41% weight reduction. A General Motors DOE-sponsored project developed an integrated die-cast magnesium door inner, resulting in a nearly 50% weight reduction and a reduced part count. Magnesium closure designs present challenges such as corrosion mitigation, fastening, and assembly strategies.

Design strategies include CAE optimization, varying thicknesses, and rib patterns. Manufacturing and assembly processes involve adhesive bonding, hem flange joint designs, and surface treatments/coatings.

Figure List:

Figure 1: 2017 Chrysler Pacifica liftgate with highlighted magnesium die-cast inner.
Figure 2: Aston Martin Vanquish S with magnesium side door inners.
Figure 3: 2018 Jeep Wrangler with die-cast magnesium rear swing gate.
Figure 4: Comparison of integrated magnesium door inner and equivalent steel stamped door inner.
Figure 5: Mercedes SL Roadster die-cast magnesium door inner.
Figure 6: Ford's concept magnesium door inner with open architecture.
Figure 7: Integrated magnesium die-cast door inner from a DOE-sponsored project.
Figure 8: Vehicle deformation from 33.5 mph side barrier impact CAE simulation.
Figure 9: Simulated intrusion displacements from 33.5 mph side barrier impact CAE simulation.
Figure 10: Vehicle deformation from 20 mph 75° side pole impact CAE simulation.
Figure 11: Simulated intrusions from 20 mph 75° side pole impact CAE simulation.
Figure 12: Door assembly with integrated magnesium die-cast door inner from a DOE-sponsored project.

Fig. 4. Integrated magnesium door cast inner developed as part of a DOEsponsored project led by GM, right, and equivalent steel stamped door inner, left [10] (Copyright 2015 by IMA. Used with permission).

Fig. 5. Mercedes SL Roadster die-cast magnesium door inner [19] (Copyright 2004 by Indian Institute of Metals. Used with permission)

Fig. 10. Vehicle deformation resulting from 20 mph 75° side pole impact CAE simulations using a 50th percentile male crash dummy according to FMVSS 214 of the BIW structure in Ref. [9] (Copyright 2012 by CARB. Used with permission).

6. Conclusion and Discussion:

This review summarizes the weight-saving potential and performance characteristics of magnesium die-castings in closure applications. Solutions exist for the challenges of designing for stiffness, crash performance, and manufacturability, as well as for designing assembly processes, coating systems, and mitigating galvanic corrosion. Magnesium die-castings offer significant advantages for achieving future CAFE requirements through vehicle lightweighting. However, further research on galvanic corrosion mitigation strategies is needed.

7. Future Research:

Further investigation into galvanic corrosion mitigation strategies.
Research into various magnesium alloys and manufacturing processes.
Exploration of the applicability of magnesium die-castings to more complex closure systems.

8. References:

(List of references [1] through [20] as cited in the original paper)

[1] “Draft Technical Assessment Report, Midterm Evaluation of Light-Duty Vehicles Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards for Model Years 2022-2025”, EPA, NHTSA, 2016.
[2] USAMP team, Magnesium Vision 2020: A North American Automotive Strategic Vision for Magnesium, USCAR, 2006.
[3] FCA North America media, media.fcanorthamerica.com, 2017.
[4] M. Stevens, S. Modi, M. Chess, Mixed Materials Solutions: Alternative Materials for Door Assemblies, Center for Automotive Research, 2016 CAR Report.
[5] J.P. Weiler, C. Sweet, A. Adams, R. Berkmortel, S. Rejc, C. Duke, Next generation magnesium liftgate – utilizing advanced technologies to maximize mass reduction in a high volume vehicle application, in: Proceedings of the 2016 IMA World Magnesium Conference, 2016.
[6] P.J. Blanchard, G.T. Bretz, S. Subramanian, J.E. deVries, A. Syvret, A. MacDonald, and P. Jolley, “The Application of Magnesium Die Casting to Vehicle Closures”, SAE Technical Paper Series 2005-01-0338, 2005, doi:10.4271/2005-01-0338.
[7] IMA, “Magnesium Liftgate Improves Fuel Economy”, Magnesium Showcase, 12 (2010), 2.
[8] Lotus Engineering Inc., An Assessment of Mass Reduction Opportunities for a 2017-2020 Model Year Vehicle Program, The International Council on Clean Transportation, 2010.
[9] Lotus Engineering Inc., Evaluating the Structure and Crashworthiness of a 2020 Model-Year, Mass-Reduced Crossover Vehicle using FEA Modeling, California Air Resource Board, 2012.
[10] J. Jekl, J. Auld, Sweet C, J.T. Carter, S. Resch, A.D. Klarner, J. Brevick, A.A. Luo, Development of a thin-wall magnesium side door inner panel for automobiles, in: Proceedings of the 2015 IMA World Magnesium Conference, 2015.
[11] P. Jonason, P. Nilsson, and M. Isacsson, “MAGDOOR – Magnesium in Structural Application”, SAE Technical Paper Series 1999-01-3198, 1999, doi:10.4271/1999-01-3198.
[12] T. Ruden, R. Murty, and W. Ruch, “Design and Development of a Magnesium/Aluminum Door Frame”, SAE Technical Paper Series 930413, 1993, doi:10.4271/930413.
[13] C. Blawert, V. Heitmann, D. Höche, K.U. Kainer, H. Schrekenberger, P. Izquierdo, S.G. Klose, Design of hybrid Mg/Al components for the automotive body – preventing general and galvanic corrosion, in: Proceedings of the 2010 IMA World Magnesium Conference, 2010.
[14] H. Schreckenberger, M. Papke and S. Eisenberg, “The Magnesium Hatchback of the 3-Liter Car: pProcessing and Corrosion Protection”, SAE Technical Paper Series 2000-01-1123, 2000, doi:10.4271/ 2000-01-1123.
[15] H. Friedrich, S. Schumann, J. Mater. Process. Technol. 117 (2001) 276– 281, doi:10.1016/S0924-0136(01)00780-4.
[16] G.T. Bretz, K.A. Lazarz, D.J. Hill, P.J. Blanchard, Magnesium Technology, TMS, Warrendale, PA, 2004, pp. 113–119.
[17] Aston Martin global website, 2018.
[18] Daimler Global Media, media.daimler.com, 2017.
[19] C. Blawert, N. Hort, K.U. Kainer, Trans. Indian Inst. Metals 57 (2004) 397–408 doi:.
[20] K. Dziczek, M. Schultz, T. Fiorelli, B. Swiecki, Y. Chen, D. Andrea, “New Materials/New Skills for the Trades”, CAR Research, 2017.

Copyright

This summary is based on J.P. Weiler's paper: "A review of magnesium die-castings for closure applications."

https://doi.org/10.1016/j.jma.2019.02.005

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