By J.P. Weiler, Meridian Lightweight Technologies, Inc.
Editor’s Note: This is the third in a series of articles highlighting developments in the magnesium industry, with the aim of addressing trends and common misconceptions. The first two articles focused on primary production of magnesium and automotive applications, while future articles will focus on magnesium myths and sustainability.
Introduction
Whiile automotive use encompasses the majority of magnesium alloy applications, there have been, and continue to be a wide array of noteworthy applications outside of the automotive industry. These applications include consumer electronics, biomedical applications, aerospace and aviation applications, construction equipment, and handheld devices. The magnesium alloys utilized in these applications are fabricated from high pressure die-castings, sand-castings, semi-solid castings, extrusions, and additive manufacturing, among others. Beyond their lightweighting capability, some of the other key advantages of the magnesium alloys used in these applications include excellent specific heat capabilities, damping properties, flammability resistance, electromagnetic interference shielding, and strength-to-weight characteristics.
Aviation
One of the first large uses of magnesium alloys was found in aircraft applications, as magnesium was extensively utilized in aircraft development during WWI and WWII. The Convair B-36 Peacemaker, built between 1949 and 1959, had the longest wingspan of any combat aircraft ever built, was capable of intercontinental flight without refueling, and was fabricated using over 5 tonnes of magnesium.1 The B-36 utilized over 600 kg of magnesium forgings, over 5,000 kg of magnesium sheet material, and over 400 kg of magnesium castings.
Magnesium alloys have also been extensively utilized in both cast and sheet form in Sikorsky H19 transport helicopters manufactured in the 1950s (Figure 1), accounting for 17% of the total mass of the aircraft, as well as sand-castings for the transmission housings on Sikorsky UH-60 Black Hawk® helicopters starting in the 1970s until current day.2
In addition, magnesium alloys have seen recent applications in civilian aircraft seating.3 A newly developed alloy, Elektron43, which meets strict flammability resistance requirements while maximizing strength, is used in aviation structural seat applications demonstrating a significant weight reduction.4
Biomedical
Magnesium alloys have long been favored for biomedical applications due to their specific strength, low density, biocompatibility, and biodegradability. The density and elastic modulus of magnesium alloys are similar to human bone, and the corrosion rates of magnesium alloys in a physiological environment can act to stabilize and help promote bone strength during recovery from an orthopedic procedure. Several different researchers and companies have developed magnesium alloy implants and screws/pins using additive manufacturing or wire processes and have explored different surface coatings to control the corrosion rate for these applications (Figure 2).5,6 Magnesium alloys have shown satisfactory results in orthopedic applications, with the U.S. Food and Drug Administration (FDA) recently creating a designation for an expedited development and review process for approval of such applications.7
Consumer Electronics
Magnesium alloys are being utilized at a growing rate in the consumer electronics market, with applications including smartphones, tablets, and laptop computer casings, among others. Advances in manufacturing technologies have enabled cold stamping of magnesium alloy sheet material at thicknesses of 0.5 mm, while the reduced thermal conductivity and improved durability enable a favorable user experience.8
Both Lenovo and LG Electronics have implemented magnesium alloys in their laptop cases for several different models. For example, the keyboard frames in Lenovo’s ThinkPad T14 laptops are made from 90% recycled magnesium (Figure 3). The lightweighting capability in these applications is demonstrated by the achievement of several world records for lightest commercially available laptops. For example, the lightest 16-inch laptop is the 2024 LG Gram, with a weight of 1.36 kg,9 a weight savings of nearly 30% from other commercially available laptops.
Additional Applications
Magnesium alloys have also seen a wide range of use in other applications, from construction equipment to handheld detection equipment, to power and garden tools. In addition to their lightweighting capabilities in these applications, magnesium alloys offer damping capabilities, part consolidation, and electromagnetic interference shielding.
Waygate Technologies has developed a one-piece magnesium cast housing for their line of handheld remote portable borescopes. One model houses a 5.8 inch LCD display and a 6.8 Ah lithium-ion battery with a 3-hour runtime, carrying a total weight of 2.5 kg.10
Several different magnesium alloy casting applications are found in forestry machinery, including a novel lightweight piston on the Stihl MS 400 C-M chainsaw,11 which provides an increased engine performance while reducing weight. Another design is the crank case for the MS 261 C-M forestry chainsaw. Further, the Makita 5007MG 7.25 inch magnesium circular saw features magnesium alloy castings for the saw base, blade case, and safety guard of the saw, resulting in superior balancing in a lightweight application and a 20%-35% weight savings from comparable saws.12
Future Applications
The future for magnesium alloy applications looks to benefit primarily from lightweighting capabilities in novel developments. Magnesium alloy applications have excellent potential for spacecraft applications, including cast satellite brackets and electronic chassis components with an expected weight reduction of 20-30%.3 The prospect of utilizing magnesium alloys in energy storage technologies is very well researched due to its volumetric capacity and capability to store hydrogen at nearly 15 wt% by mass.3
Several researchers have demonstrated the efficient solid state hydrogen storage potential of magnesium alloys.13 However, further development of related infrastructure is needed to fully realize the potential.
Finally, magnesium alloys have a very promising future in new developments in aerial applications, such as unmanned aerial vehicles (i.e. drones) or electric vertical take-off and landing (eVTOL) aircraft that require significant use of lightweight materials to maximize flight characteristics.
As this overview illustrates, magnesium alloys have seen a wide range of applications in consumer electronics, biomedical applications, aviation applications, and power and handheld equipment and have a large potential future in hydrogen storage, aerial, and other future transportation modes.
Editor’s Note: This article first appeared in the August 2024 issue of Light Metal Age. To receive the current issue, please subscribe.