Introduction
In the manufacturing industry, product weight reduction is an essential challenge for improving fuel efficiency, performance, and cost savings. Particularly in the automotive, aerospace, and precision machinery sectors, aluminum and magnesium alloys are widely used as representative lightweight materials. However, each has unique characteristics, and the optimal material cannot be chosen based on a simple weight comparison. This article is intended for Japanese manufacturing executives and procurement managers, providing a detailed comparison of aluminum casting (hereinafter, aluminum casting) and magnesium casting (hereinafter, magnesium casting) from the perspectives of lightweight properties, strength, and the all-important cost. We will clearly explain specialized casting technologies and material properties using specific data and examples to support your optimal decision-making in product development.
Weight Reduction: Magnesium Holds a Decisive Advantage
When product weight reduction is the highest priority, magnesium casting offers a significant advantage over aluminum casting. This is due to the difference in specific gravity between the two. While the specific gravity of aluminum alloys (e.g., ADC12) is approximately , that of magnesium alloys (e.g., AZ91D) is approximately , boasting an astonishing lightness of about two-thirds that of aluminum.
Significant Benefits Achieved with Unrivaled Lightness
This difference in specific gravity has a profound impact not only on individual components but also on the weight reduction of the entire system. For example, replacing parts like a car’s transmission case, steering wheel, or an aircraft’s gearbox housing with magnesium alloys enables dramatic weight reduction. This directly translates to improved vehicle fuel efficiency and extended cruising range, while also reducing the moment of inertia of moving parts, which is expected to improve equipment responsiveness and vibration characteristics.
Furthermore, magnesium alloys have a cutting resistance of about half that of aluminum, making them highly machinable. This allows for reduced processing time and extended tool life, contributing to improved production efficiency. In addition, their low molten viscosity allows for the molding of extremely thin-walled parts, such as those with a thickness of , providing greater design freedom for further weight reduction.
Strength and Durability: The Key is to Use Their Characteristics According to the Application
In terms of strength, aluminum and magnesium have different characteristics, and the optimal choice varies depending on the application. Generally, aluminum alloys tend to have an advantage in tensile and fatigue strength, but magnesium alloys are characterized by a very high specific strength (strength per unit density).
Aluminum’s Toughness vs. Magnesium’s Rigidity
With a tensile strength of approximately and an elongation of 1-10%, aluminum alloys are excellent in toughness. This means they can absorb energy by deforming plastically upon impact and are less likely to fracture. For this reason, they are suitable for crash zones and structural components under high stress.
On the other hand, while magnesium alloys have lower tensile strength than aluminum, they have a very high specific rigidity. This means they are lightweight yet resistant to bending, making them advantageous for parts that require rigidity. They also have excellent vibration damping capacity, making them suitable for motor housings and electronic equipment enclosures where repetitive vibrations occur, contributing to extended equipment life and noise reduction.
<div class=”data-box”>Key Data: Comparison of Aluminum and Magnesium Properties– Specific Gravity: Aluminum approx. 2.7g/cm³ vs. Magnesium approx. 1.8g/cm³- Cutting Resistance: Magnesium is approx. 1/2 of aluminum- Thin-Wall Molding: Magnesium can be molded to 0.5mm (Source: Taiyo Parts)- Tensile Strength: Aluminum Alloy approx. 320MPa vs. Magnesium Alloy approx. 240MPa (Source: Aludiecasting)- Fatigue Strength: Magnesium Alloy 70-150MPa (Source: Aludiecasting)
Source: The difference between magnesium die-casting and aluminum die-casting
Cost: The Difference in Price Hikes and Production Processes
Magnesium casting tends to be more expensive than aluminum casting in terms of material cost. This is due to the cost of refining magnesium and the special nature of the casting process. However, the decision should not be based solely on material costs.
High Cost Factors of Magnesium and the Potential for Total Cost Reduction
Magnesium is highly reactive and readily oxidizes in the presence of air, requiring special melting furnaces and work in an inert gas atmosphere during casting. This increases capital investment and running costs, which are reflected in the product price. However, this initial cost can potentially be offset by subsequent cost reductions throughout the product’s life cycle.
As mentioned earlier, magnesium’s excellent machinability can lead to savings in labor costs and tool costs through reduced processing time. Furthermore, the weight reduction in the final product contributes to a total cost reduction throughout the product’s life cycle, in the form of improved fuel efficiency and lower transportation costs. Magnesium alloys are also highly recyclable, which holds the potential for future cost reductions.
Demand Trends in the Automotive Industry
The Japanese die-casting market has seen a decrease in production volume due to the downturn in demand from the automotive industry, but the market value is increasing. This suggests a growing demand for high-value-added die-cast parts. With the advancement of vehicle electrification (EVs), the need for weight reduction to compensate for the increased weight from batteries is growing more than ever. The demand for magnesium used in automotive parts is projected to more than double from 2016 to 2026, indicating the increasing importance of magnesium casting in the future.
Conclusion
Both aluminum casting and magnesium casting are excellent lightweight materials, but their properties and suitable applications are clearly different. Magnesium casting is the optimal choice for parts that require extreme weight reduction, with a specific gravity of about two-thirds that of aluminum. Its high specific strength and vibration damping capacity also make it advantageous for electronic equipment and moving parts where rigidity and durability are crucial. On the other hand, aluminum casting, with its high toughness and excellent corrosion resistance, is suitable for structural parts and crash zones that require shock absorption.
In terms of cost, magnesium tends to be more expensive than aluminum due to its material price and the specialized casting process, but it is necessary to consider the total cost reduction effects from its excellent machinability and the weight reduction of the final product. The increasing need for weight reduction in the automotive industry, in particular, is driving the expansion of the magnesium casting market.
The key to increasing your competitiveness is to clearly define what you value most in your product development—whether it’s weight reduction, strength, or cost—and then understand the characteristics of each material to make the optimal choice. At Daiwa Aluminum Vietnam, we have a deep understanding of these properties and propose the best casting solutions to meet your diverse needs.