Tohoku University, Japan, announces that a newly discovered magnesium-scandium alloy with a bcc structure shows a martensitic transformation and exhibits the superelastic effect at −150°C (−238°F). The Mg-20Sc alloy was confirmed to exhibit a superelastic strain of over 4%, and shows 6% recoverable strain (including both ordinary elastic and superelastic strain). The image shows the stress-strain curve of the Mg-Sc alloy sheet at −150°C (−238°F). The sheet specimen was loaded in tension up to a strain of 3% and then unloaded. The alloy sheet shows a superelastic effect.
In addition, a shape memory effect was observed. The team found that the operating temperature of a Mg-Sc shape-memory alloy can be varied by controlling scandium content, and confirmed that a Mg-Sc alloy with 18.3 at% scandium showed shape recovery upon heating from −30°C (−22°F) to room temperature. The Mg-Sc SMA has a density of about 2 g/cm3, which is one-third less than that of practical TiNi SMAs.
The researchers believe that this could have a significant impact on the aerospace industry. The lighter the components, the more fuel efficient the rockets and spacecraft. So this lightweight magnesium-based SMA has great potential in aerospace applications such as self-deployable space habitat frames and damping devices on spacecraft systems.
Moreover, magnesium-based SMAs can also be applied in the medical field. Currently, TiNi superelastic alloys are being used as self-expandable stents with great success. However, there is the problem of in-stent restenosis. To overcome the restenosis, biodegradable magnesium alloy stents have recently been proposed. This means that the Mg-Sc superelastic alloy could potentially be applied in biodegradable self-expanding stents.
The researchers expect that in the future, the alloy composition will be optimized to increase the operating temperature, and the biocompatibility and biodegradable characteristics of the present alloy system will be evaluated.
http://www.tohoku.ac.jp/en/press/new_lightweight_shape_shifting_alloy.html
