A research group of Dr. Yukiko Ogawa, Associate Professor Yuji Sudo, Assistant Professor Daisuke Ando, and Professor Junichi Koike of the Graduate School of Engineering, Tohoku University has succeeded in developing a magnesium (Mg) alloy that exhibits shape memory characteristics.Its specific gravity is about 1/3 that of conventional shape memory alloys. It was published in the American scientific journal "Science" dated July 7nd.
Shape memory alloys have the characteristics that they return to their original state even if they are deformed at a certain temperature, and they return to their original state when they are heated to a certain temperature after deformation.It is widely used from familiar items such as eyeglass frames to medical products, and in recent years, it has been attracting attention as a vibration absorbing part for rockets and spacecraft, which is said to reduce the cost by 1 million yen if it is reduced by 100 kg.
So far, the research group has divided the Mg-Sc alloy, which is magnesium (Mg) plus scandium (Sc), into a body-centered cubic structure (bcc) in addition to the dense hexagonal structure (hcp), which is the crystal structure of conventional Mg alloys. Focusing on the fact that it also has the structure of, we have been studying the high functionality of Mg alloys by utilizing its properties.
In the process of research, we found that the Mg-Sc alloy has an excellent balance of high strength and high ductility compared to the conventional Mg alloy with hcp crystal structure, and this time, the bcc type Mg-Sc alloy is martensitic transformation. It was discovered that the phase transformation was caused and the shape memory characteristics were expressed. It was confirmed that the Mg-20 at% Sc alloy exhibited superelastic strain of 150% or more at a low temperature of minus 4 ˚C.Shape memory characteristics have been found in various alloy systems so far, but it is said that this is the first report on an ultra-lightweight alloy mainly composed of lightweight elements such as magnesium.
Shape memory Mg alloy, which is about 70% lighter than conventional alloys and has excellent strength and ductility, can reduce the weight of members without impairing strength, and is used in the aviation and space industries, especially at low temperatures. It is highly expected to be applied as a space material.In addition, since magnesium has biodegradability, it is expected that new high-performance stents such as biodegradable superelastic magnesium stents will be applied in the medical field.
In the future, it is planned to evaluate the increase in operating temperature by optimizing the alloy composition and the biocompatibility of this alloy for practical use.
