Anisotropic Fatigue Behavior of Magnesium Alloys Investigated

ENVIRONMENTAL protection has surfaced as a major problem that the world needs to solve, and there is no doubt that car pollution takes up a large portion of it. Therefore, the need for eco-friendly cars or ‘Green cars’ with lower emissions and more fuel efficiency is has increased, which explains why the recent work on the related subject conducted by POSTECH and the Korea Research Institute of Standards Science (KRISS) is gaining significance. It has been reported that Professor Chong Soo Lee and Sung Hyuk Park, a Ph.D. candidate of POSTECH have made a discovery in their research which strengthened the possibility Green car development. In joint research with Dr. Seong-Gu Hong and Dr. Yong-Hak Huh of KRISS, they have identified the anisotropic cause for the fatigue characteristics of magnesium alloy (rolled Mg-3Al-1Zn) for the first time.

Magnesium alloy is a metal becoming increasingly popular due to its merits in light weight, especially for transportation equipments. It is being called an eco-friendly material because it is both stronger and lighter compared to other metals: about one-third lighter than aluminum and two-thirds lighter than steel, and therefore needs less fuel. According to Professor Lee, the usage of magnesium parts can reduce the weight of the car by approximately 10 percent, which allows it to become 6 to 8 percent more fuel efficient. The automobile industry is currently making huge efforts to utilize the alloy in the fabrication of motor vehicles by inserting hybrid, fuel cell and other automotive technologies, and parts made of magnesium alloy are considered as the key element to the completion of Green cars.

However, magnesium alloys have not been widely commercialized in the automobile industry because the research work on fatigue behavior has not yet been advanced enough. Fatigue behavior, which is related to the prediction of how the properties of metal react to stress and time, is critical as it influences the durability of the metal. The research in this area was hindered because of the twin deformation and columnar texture properties of magnesium.

The POSTECH-KRISS joint research team performed various fatigue tests of magnesium alloys and found that magnesium has anisotropic fatigue characteristics. Moreover, they identified a change in the fatigue behavior depending on the loading direction. This work is fundamental in the sense that it may lead to the elevation of the fatigue characteristics. The team has submitted a patent application for a technology that allows them to augment the life and durability of magnesium by approximately 48 percent.

Professor Lee stated that the fatigue behavior of magnesium alloy is a critical property that affects the safety of passengers. He also added that this research accomplishment by POSTECH and KRISS would vitalize the Green car industry and other eco-friendly manufactures, and that the joint research team plans to work to commercialize the promising metal. The study appeared in the Journal of Materials Research as the cover paper of the May 2010 publication.