February 2023 Volume 5

MATERIALS

The Potential for Magnesium Forgings in Automotive By Andrew Halonen

characteristics, which are critical for customer comfort, a major factor in how customers perceive vehicle quality. Under the dashboard, welded steel is the most common material used to produce the cross-car beam. However, some steel-intensive vehicles (such as the 2019 Acura RDX) use one-piece magnesium die castings for the cross-car beam, because they meet both the crash and structural needs, while reducing weight. Another key benefit of magnesium die castings is their single-piece construction, which eliminates the tolerance stack-up issues common with welded structures. A similar application is the structure for the dashboard or console, which is situated between the front seats and the center stack below the radio. These console structures are often comprised of magnesium produced with the HPDC process. In addition, magnesium has found success in seat frames, as they represent a lighter weight alternative to steel. As can be seen by these examples, magnesium is primarily used for interior applications. There are three primary reasons for this—the structural performance of the magnesium is sufficient for these components, the components are able to provide lightweighting benefits, and interior components do not come into contact with the corrosive road salts that require additional coatings. In the production of magnesium castings, AZ91 is most common for structural components and covers due to its high strength and moderate elongation. For those components in the crush zone that must deliver crash worthiness, AM50 and AM60 are more common because the elongation of these is 10-15%, which is a critical attribute for energy absorption. All of these alloys are readily available. They are produced as primary magnesium (mostly via the low-cost Pidgeon process) or are supplied through recycling shops here in the U.S. The outlook for magnesium die castings is very good. According to Ducker’s presentation in August 2021, the average amount of magnesium castings used in vehicles will grow from 3.6 kg per vehicle in 2016 to 11.5 kg per vehicle in 2030. The die castings that have been noted here, along with door inners, will make up the majority of this growth.3 The current use of magnesium forgings in automotive is severely limited. The main use of magnesium forgings is the production of wheels. Magnesium seems to be a natural fit for wheel production, since having lighter wheels provides a number of benefits. The lightest weight wheel ensures the least rolling resistance, maximum efficiency for acceleration and braking, and the best fuel economy. Currently, forged magnesium wheels are available for racecars and

In the world of product development, many materials are available to pick from, yet companies tend to play to their favorites. In metals, these materials range from exotic to common, from low density to high, and they are processed into different forms.The majority of car components—from the body panels to the protective rockers to the suspension arms—are made of aluminum, steel, or iron. Where does magnesium fit into this conversation? Magnesium metal is the lowest density metal and is far from rare, as it is the eighth most abundant element in the Earth’s crust and the third most plentiful element in dissolved seawater.1 Magnesium has been available for centuries and can be processed into a variety of forms, including castings, extrusion, sheet, and forgings. However, despite being a low-density material that could be valuable in automotive, it is not often included in the lightweighting conversation. This article will explore the metal’s current use in automotive and its potential Magnesium is primarily used by aluminum and steel producers as a critical alloying element in the production of automotive components and other products. Altogether, alloying represents over 50% of the global demand for magnesium. Outside of alloying, the next major market for magnesium is the production of near net shape castings. For example, magnesium is one of the common materials used to produce the structural steering wheel frame, primarily because it is easy to high pressure die cast (HPDC).2 The circular shape of the steering column is inherently stiff, which makes up for the low stiffness (modulus) of magnesium. Magnesium alloys also perform well for the energy absorption, which is a major requirement for providing passenger protection in a vehicle crash. In addition, magnesium has good vibration damping value in the production of forged car components. Current MagnesiumUse in Automotive

FIA MAGAZINE | FEBRUARY 2023 36