What is a magnesium alloy?
Magnesium is one of the lightest metals used as structural materials, with a specific gravity that is two thirds that of aluminum and one fourth that of steel. Magnesium has high strength per weight (specific strength) and thus has advantages in reducing weight of parts, while having disadvantages in machining workability and corrosion resistance. Therefore, metal manufacturers add various elements to improve properties to fit their own use. AZ91 magnesium alloy is designed to increase corrosion resistance by adding 9% of aluminum and 1% of zinc and is widely used, mainly among car parts manufacturers. However, with total 10% of added elements, the AZ91 alloy presents difficulties in rolling and pressing, thus so far has been used only for cast parts (by die casting*) that do not require pressing. To expand its applications, the AZ91 alloy should be adaptable to press parts.
What are the features of the magnesium alloy?
By applying its unique continuous casting technology, process control technologies in manufacturing of electric and special steel wires, and material analysis technologies, Sumitomo Electric successfully reduced the size of crystal structure of AZ91 alloy to 1/10 to the conventional structure and developed a technique to process sheet materials, becoming the first company in the world to succeed in manufacturing AZ91 sheet materials that are workable for pressing. In addition, the company continues developing the warm pressing, bonding, and surface treatment technologies that will be necessary to produce structural membrane made of AZ91 alloy. The company has already started mass production using warm pressing.
- Tensile strength
- The specific strength is one of the highest among the practical metals, due to the increased strength by rolling processing.
- Thanks to light specific gravity, by optimizing thickness, both light weight and stiffness are achieved.
- Corrosion resistance
- The highest level of corrosion resistance in magnesium alloys is achieved.
- Warm molding process enables deep-drawing similar to that of steel sheet.
- Coating properties
- General processing, such as surface treatment and coating, is applicable.
- Remelting and recycling requires less energy than iron and aluminum.
While trying to expand the market for AZ91 alloy products that are already available in mass production, Sumitomo Electric is developing new magnesium alloys that have different properties from AZ91 alloy. For instance, the company has already developed several magnesium alloys that have overcome the weaknesses in properties compared with aluminum and iron, such as a non-combustible magnesium alloy that enables safer cutting and polishing and a highly formable magnesium alloy that has better workability in warm pressing. Sumitomo Electric will continue developing new magnesium alloys that satisfy customers’ requirements, while proposing and expanding the use of magnesium alloys as an environment-friendly material that may replace iron and aluminum.
Planning & Administrative Department
What responses have you had from customers?
Sumitomo Electric’s AZ91 alloy sheets have higher tensile strength and corrosion resistance compared to similar AZ91 alloy die cast products. Our customers appreciate its properties of high rigidity and good external appearance and use it as a body part in laptop PCs and mobile phones.
Also our customers recognize the better formability of the AZ91 alloy sheets compared with aluminum alloy sheets in forming complex shapes in warm pressing and potentially wider applications as structural components.
What further applications are expected for magnesium alloy?
The transportation sector including automobile, railway, and aircraft is particularly seeking lighter car and body components to improve fuel efficiency and travelling performance. Already several car manufacturers have adopted magnesium alloys for engine and transmission parts and the growing demand is expected.