**7. Conclusions: new trends and perspectives**

The historical and current primary market for structural applications of magnesium alloys is high-pressure die-cast parts. We find those components in the automobile's powertrain, chassis, or body areas. Depending on the type of structural part to shape, key technical features that need to target are the safe-at-break behavior avoiding fast-fracture failure modes, sufficient toughness (i.e., minimum impact energy to rupture and fracture toughness), specific strength, corrosion resistance, high-temperature resistance, or creep resistance (for powertrain applications). From the manufacturing point of view, the requirements addressed shall target affordable production cost, which merges fixed and variable costs, derived from the accounting of investment costs (machinery and tools, energy, labor, etc.) and operating costs (raw material cost, trimming, machining, coating costs, etc.) to recoup.

Specifically, in automotive assemblies, corrosion concerns are crucial. Today high purity versions of magnesium alloys show corrosion properties comparable to aluminum die casting alloys, but galvanic corrosion problems persist when magnesium parts have to be assembled with different materials. Therefore, advancements in coating techniques are the basis for safely combining magnesium parts with other materials. High ductility magnesium alloys are of interest to the automotive sector. Advancements in alloying are crucial for the correct choice of the structural ability of magnesium material. The higher creep resistance of Mg-Al-Si, the AS series, acknowledged by Germans during WII, is allowed by Si addition which forms fine and hard Mg2Si particles along the grain boundaries to help retard grain boundary sliding. The remarkable grain-refining ability of zirconium in the Mg-Zn-Zr series alloys allows high strength and ductility for use either at elevated temperatures or for energyabsorbing applications, however at a higher cost due to Zr. The ZE series achieved further mechanical properties in the die-cast part with Mg-Rare Earth-Zn-Zr casting alloys. RE elements (La, Ce, etc.) are added as they are active during aging treatment by promoting high-temperature stable precipitates with a strengthening effect. The costly Magnesium-Yttrium casting alloys, the WE series, containing approximately 4–5 wt.% Y, exhibit high strength with good creep resistance at temperatures up to 300°C and superior corrosion resistance (comparable to some aluminum-based casting alloys). Furthermore, the WE43 and the Elektron 21, a proprietary magnesiumbased casting alloy containing neodymium, gadolinium, and zinc developed by Magnesium Elektron (today part of Luxfer MEL Technology), passed stringent flammability tests of Federal Aviation Administration FAA-FAR 25.853 Part 25, Appendix F, Part 2 Modified Seat Cushion Test. Both alloys did not burn when melted, or they are self-extinguished.

More cost-efficient production routes for sheet products are believed to create new opportunities for the automotive market segment. Considerable efforts have been directed at innovative developments of global efforts in expanding the manufacturing capabilities of magnesium sheets through the twin-roll casting process route, offering many benefits, including a reduction in the number of processing steps and energy savings [42].

Finally, last but not least, die-casting and semisolid process design strategies are similar to those employed for injection molding of structural plastics. But, in general, plastic designs require thicker sections than magnesium die-castings. Both materials allow complex shapes with ribs to enhance stiffness (**Figure 14**), but magnesium die-castings need more minor material for these features than plastics. As a result, magnesium die-castings can be designed more efficiently (less volume, less weight, more significant feature variation) and offer a higher degree of definition than comparable plastic designs, superior mechanical properties, and the capability to integrate several functional design features, material recyclability. The latter feature is not of minor importance, being automakers sensitive to recyclability resources of material used for car manufacturing. Although the material price-based approach leads to the obvious choice of plastics, complex and large parts could present unforeseen internal costs to the product line, negatively impacting final product marketability. A whole approach cost also considers the impact on a company's internal costs structure and the value-added needs of the next customer in the product chain, up to and including the end-user. In a total system cost strategy, the benefits of using magnesium tend to outweigh the lowest material price strategy. This is typical for products like instrument panel structures. The benefits of higher stiffness, elongation, toughness, and design flexibility allow the magnesium part to readily integrate many features in a one-piece to be fully assembled and quickly installed into the vehicle with weight-saving up to 50% compared to plastic designs.

*Magnesium Alloys for Sustainable Weight-Saving Approach: A Brief Market Overview, New… DOI: http://dx.doi.org/10.5772/intechopen.102777*

### **Figure 14.**

*Magnesium AM 50 die cast front center console for Audi A8, high stiffness, no machining and all connection and fixing points are intergrated (courtesy of GF Casting Solutions).*

An interesting overlap of cast magnesium's mechanical and physical properties with reinforced plastics, primarily strength, and density, would drive the material switch. In the interior design of automotive vehicles today, large bodies are made of non-fully recyclable plastics. Thus, other potentialities for magnesium die-casting and injection molding could be redesigning today's plastic structural components with recyclable and more robust magnesium metal.

In this chapter, we tried to resume the magnesium for lightweight approach over the past, till today. Hopefully, but not exhaustively, this was tentative to answer where the magnesium industry is going. We must not forget the past, learning lessons that are still valid today. However, we must consider some new factors, mainly based on the magnesium trade, were unknown in the past century or during the golden Age of magnesium peak demand. It is a fact that when going through magnesium history, several articles projected an optimistic future for magnesium.

Forecasting the future of magnesium, especially in current pandemic times, is difficult. Nevertheless, one aspect appears clear by going through past and recent magnesium history: magnesium had survived continuous fluctuating demand;

meanwhile, price volatility registered over time depended on the current (nonstructured and programmed) supply capacity over time and trade issues.

Several concerns about magnesium's potential applications are today derived from false myths. Eighty years ago, Germans and (after) Americans employed magnesium for aircraft weight-saving, but today it is wrongly thought there are few proofs of its capabilities in realizing lightweight bodies. What is clear from the lesson learned in the past (and today) is that it is necessary to dramatically increase the primary magnesium supply with modern low impacting big plants. Looking at recent history, we are probably on the right track. As learned from the past, prices are not volatile once the supply is stable, and the magnesium's demand (driven by automakers primarily) rises.
