Metal part manufacturers form alloys by mixing two or more molten metals, or a molten metal with a nonmetal. The combination permits the resulting mixture to display properties supplied by all the constituents. Many different alloys contribute to metal components in the marketplace today. Magnesium alloys have assumed increasing importance recently.
Purified magnesium forms a strong, silvery-white very lightweight metal. Both malleable and ductile, it produces a brilliant white light when burned. Magnesium occurs abundantly in nature combined with other materials.
For centuries, this metal proved difficult to handle and process due to its combustibility. As metallurgists have learned more about the production of useful magnesium alloys, the demand for products containing this lightweight metal has increased. Today, parts manufacturers frequently form magnesium alloys using combinations of aluminum, silicon, copper, calcium, zinc, manganese and other elements.
Designating Magnesium Alloys
Many manufacturers designate magnesium alloys by relying upon a classification system set forth in specification B275 of the American Society for Testing and Materials International ("the ASTM"). This system employs a convenient shorthand for describing metal alloys. It uses capital letters to refer to elements, and numbers to refer to percentage weights of the constituent alloys. Manufacturers must confirm designated alloy formulations when utilizing the ASTM system.
Magnesium alloys today fall readily into three main varieties: cast alloys, wrought alloys and named proprietary alloys owned by specific companies or patent holders:
Cast aluminum alloys encompass the majority of commercially utilized magnesium alloys. Some magnesium alloys permit die casting, sand casting and permanent mold casting.
One example of a cast magnesium alloy utilizes the shorthand designation AZ91. It consists of magnesium combined with 9% aluminum and 1% zinc. In this alloy, the addition of aluminum and zinc both contribute to the hardening of the metal. Some magnesium alloys in this category use silver. Recently manufacturers have developed cast magnesium alloys incorporating rare earth metals, such as yttrium.
The wrought magnesium alloys employed commercially by manufacturers display enhanced tensile proof strength. Some widely used wrought alloys include: AZ31, AZ61, and ZK60. The first two alloys rely on combinations of aluminum and zinc, and the latter depends upon zinc and zirconium.
Proprietary alloys span both of the other two categories. Some cast readily, while others work well as wrought alloys. These magnesium alloys have received specific names, usually conferred by the inventor or patent holder. The Elektron magnesium alloys manufactured by Magnesium Elektron Limited illustrates this grouping.
Properties And Applications of Magnesium Alloys
Magnesium carries the atomic number of 12 and falls within Group 2A on the Periodic Table as an alkaline earth metal. The physical properties of this element contribute significantly to popular magnesium alloys. In many situations, these alloys provide excellent alternatives to aluminum, another lightweight metal widely utilized for commercial purposes.
Light in weight, with excellent ductility and malleability, magnesium alloys have found widespread application within the aerospace and aviation industries. The brilliance of burning magnesium has allowed this metal to play a prominent role in pyrotechnics and the production of flares. Recently, manufacturers of some high-end performance automobiles have begun using magnesium alloys selectively in automotive engines and auto bodies to produce lighter weight vehicles. Some metal roof manufacturers have used magnesium and zinc alloys to create strong, lightweight roofing. Magnesium alloys have also found a growing number of applications within consumer sports and outdoor equipment manufacturing; they help form components in archery arrows, golf clubs and camping gear.
Advantages of Magnesium Alloys
Although the metal magnesium proves difficult to work with in a pure form due to its combustibility, magnesium alloys have gained widespread use in numerous commercial settings. Depending upon the constituent alloys, these products often combine reasonable strength with very low densities. They provide utility for designers seeking to reduce product weights in order to optimize fuel efficiency and lower transportation costs.
Magnesium also offers the advantage of appearing abundantly within the natural world. Unlike some metals, it occurs frequently in combination with other elements in the Earth's crust. In the future, the costs involved in extracting magnesium for use in magnesium alloys may decrease.