Recent Advances in High Performance Non-Flammable Magnesium Alloys for Wrought Applications

As magnesium alloys have the lowest density among structural metals, they have been always considered as the primary candidate for weight reduction in the fields of automobile, aerospace, electronics industry, etc. However, the poor resistance against ignition and corrosion and considerable high cost compared to competitive metals such as steels and aluminum alloys make believe magnesium is an unsafe, unreliable and expensive metal. Many efforts have been made especially into the development of new alloys and processes to control of a fundamental nature of magnesium.

Recently new non-flammable magnesium alloys with high reliability and safety and excellent performance have been developed at the Korea Institute of Materials Science, Republic of Korea, and they are considered to be applied to the body and interior parts of city trains and high-speed trains as well as automotive components and electronic devices. They don’t have to contain a harmful Be element for preventing the oxidation of magnesium and can be produced through environmental-friendly processes without the use of SF₆ gas. It has been confirmed that in combination with calcium, the selective addition of only small amount (approximately 0.2wt.%) of rare earth with relatively high solubility limit in a-Mg matrix led to significant increase in ignition temperature and corrosion resistance. Recently, mass production of ingots of the non-flammable magnesium alloys becomes possible.

In addition, the development of new classes of non-flammable wrought magnesium alloys with high workability and superior mechanical properties is in progress. They can be successfully produced by the high speed extrusion process and the twin-roll strip casting and subsequent rolling process. High strength non-flammable magnesium alloys with strength more than 400 MPa for the application of aircraft cabin can be also produced by the extrusion process under the conditions of low temperature and low extrusion speed.