The forging process of
magnesium alloys is one of the most important technologies in modern industrial production. With its lightweight nature, high strength-to-weight ratio, and excellent fatigue resistance, magnesium alloys hold great potential in various industries such as automotive, aerospace, military, and electronics. Despite the significant advantages of magnesium alloys, forging them poses numerous challenges, requiring precise control of the process to ensure that the quality and performance of the forged parts meet the required standards. This article provides a detailed analysis of
magnesium alloy forging methods, mold requirements, lubrication choices, post-forging cooling, application fields, and key control points to highlight the core technical elements and optimization strategies for practical applications.
There are various processing methods for magnesium alloys, making them suitable for different forging techniques. Common methods include extrusion, closed-die forging, and free forging in a shaped anvil. Extrusion is often used to manufacture parts requiring high structural strength and complex shapes, such as automotive wheels and aerospace components. Closed-die forging is ideal for mass production of high-precision forgings, especially for parts with complex designs and high stress requirements, such as aircraft landing gear struts and automotive chassis components. Free forging is more suited for small-batch, customized parts, especially when large dimensions or special shapes are needed.
Though magnesium and aluminum alloys share similarities in forging processes—such as forging design, mold design, and machining allowances—there are notable differences due to magnesium’s lower plasticity and poorer fluidity. Magnesium alloys have a narrower processing window, demanding more precise temperature control compared to aluminum alloys. For example, the web thickness of magnesium alloy forgings, such as MB15 and MB7, is often slightly larger than that of aluminum alloy forgings to ensure mechanical properties. Additionally, due to the lower fluidity of magnesium, certain die forging processes are limited. Large and complex forgings may require preforming through free forging followed by single-groove die forging to ensure complete material filling and shape accuracy.
Due to the excellent thermal conductivity of magnesium alloys, they cool rapidly upon contact with cold molds during forging, which can lead to surface cracks. Therefore, preheating the molds is critical. To avoid heat stress buildup during forging, molds are usually preheated to near the forging temperature (typically 250°C to 300°C), especially for large-area contact, such as in large die forging or ring rolling molds.
Lubricant selection is also crucial for successful magnesium alloy forging. Magnesium has a high coefficient of friction at elevated temperatures, requiring an even and thin application of lubricants. Common lubricants include oil-based graphite or water-based colloidal graphite. These not only reduce friction during forging but also minimize wear and ensure a smooth surface finish on the forged part.
Post-Forging Cooling and Trimming
The cooling rate of the forged part directly affects the microstructure and performance of magnesium alloys. Air cooling is commonly used to prevent microstructural changes that could result from rapid cooling. In some foreign processes for high-performance magnesium forgings, water quenching is applied immediately after forging, which is critical for age-hardened magnesium alloys to prevent the precipitation of hardening elements and ensure optimal mechanical properties during subsequent aging treatment. Trimming is usually performed at temperatures between 200°C and 300°C, and when using a bandsaw for trimming, the cooling rate must be controlled to prevent cracking due to excessive temperature differences.
The automotive industry is one of the largest application areas for magnesium alloy forging. The lightweight advantage of magnesium alloys supports efforts to reduce vehicle weight and improve fuel efficiency. For example, forged magnesium alloy wheels are denser and more impact-resistant than traditional cast products. Additionally, magnesium alloys are widely used in the aerospace industry, where landing gears, support structures, and other critical components requiring lightweight and high strength are commonly made from magnesium forgings.
Magnesium alloy forgings also have applications in military equipment, electronic devices, and sports equipment. In military applications, magnesium alloys are used to create lightweight, high-strength parts such as missile bodies and fighter jet components. In electronics, the excellent thermal conductivity and electromagnetic interference resistance of magnesium alloys make them ideal for manufacturing laptop and smartphone casings.
The success of magnesium alloy forging largely depends on precise control of deformation rate and temperature. Magnesium alloys are highly sensitive to deformation speed; excessive deformation rates can significantly reduce plasticity, increasing the risk of cracks and defects. To prevent grain growth and ensure uniformity and stable performance, complex forgings often require multiple forming steps, with the temperature gradually reduced after each step.
The forging temperature range for magnesium alloys is relatively narrow, typically between 290°C and 415°C, and must be adjusted according to the alloy type and product requirements. For example, zinc-rich ZK60 alloys require higher forging temperatures to ensure sufficient material flow and mechanical properties.
For directly cast billets, the grain structure must be pre-treated to avoid performance degradation from oversized grains during forging. Adding rare earth elements such as neodymium and yttrium to the alloy can significantly improve the microstructure, refine grains, and enhance the forging properties of magnesium alloys.
Magnesium alloy forging offers great potential and technological challenges in light of the increasing demand for lightweight, high-performance materials. By selecting appropriate forging methods, optimizing mold design, and precisely controlling temperature and deformation rates, the issues encountered in magnesium alloy forging can be effectively addressed, significantly improving the quality and performance of the forgings. As magnesium alloy technology continues to evolve and processes improve, this forging method is expected to see widespread application in high-end fields such as new energy vehicles, satellite components, and precision instruments.
