AWS WHC-5.02:2015

Magnesium and Magnesium Alloys
Scope : Magnesium alloys are used in a wide variety of applications when light weight is an important requirement. Structural applications include industrial machinery, materials-handling equipment, commercial products, and numerous components used in the aerospace, automotive and medical fields.1, 2 Magnesium alloys are ideal for use in components of industrial machinery, such as textile weaving machines and printing machines that operate at high speeds and must therefore be lightweight to minimize inertial forces. Examples of materials-handling equipment are dock boards, grain shovels, and gravity conveyors. Commercial products include luggage, ladders, and cases for electrical or electronic devices, such as mobile phone and computer cases. Magnesium alloys have high specific strength and stiffness, making these alloys particularly useful for aerospace applications in which weight savings are paramount. For similar reasons, magnesium is used in the manufacture of automobile components: wheels, body panels, seat frames, engine blocks and cradles, and gearbox housings. The properties of magnesium are also beneficial when used in biodegradable medical implants, which are designed to corrode within the body over a specific period of time. When weight is a design consideration, magnesium is most often compared to aluminum, as both are considered low-density materials; however, magnesium is considerably less dense than aluminum, i.e., (?Al = 2.70, ?Mg = 1.74 specific gravity). This translates into a lighter-weight metal. When compared to aluminum, limitations to the use of magnesium are strength, cost, formability, and corrosion resistance. Magnesium alloys are not as strong or stiff as aluminum and they are more costly, less formable, and highly susceptible to galvanic corrosion. Thus, choosing magnesium over aluminum for a specific application requires a very strong incentive to minimize weight. (For comprehensive information on welding, brazing, and soldering of magnesium and magnesium alloys, refer to the resources listed at the end of this chapter.)