A team of researchers at Tohoku University, in Japan, has discovered a magnesium-scandium (Mg-Sc) alloy with shape-memory properties that they say shows the potential for applications across a number of industries, including aerospace.

Shape-memory alloys (SMAs)—including those among the Au-Cd and NiTi-, Cu-, Fe-, Ni- and Co-based polycrystalline alloys—show distinctive behaviors such as superelasticity and shape recovery upon heating. However, these traits generally do not appear in lightweight alloy systems, such as Mg and Al alloys.

The alloy's low density could give it application in lightweight aerospace components, such as damping devises on spacecraft systems. Image credit: NASA.The newly discovered Mg-Sc alloy, with a body-centered cubic structure, shows a martensitic transformation and accordingly exhibits superelastic effect at -150 degrees Celsius. The alloy was confirmed to exhibit a superelastic strain of over 4% and therefore a 6% recoverable strain (including both ordinary elastic and superelastic strain).

In addition to its superelasticity, shape-memory effect was observed. The team found that the operational temperature of the Mg-Sc alloy can be varied by controlling the scandium content, confirming that an Mg-Sc alloy with 18.3% scandium showed shape recovery upon heating from -30 degrees Celsius to room temperature.

The researchers report that the Mg-Sc alloy has a density of about 2 g/cm³, which is one-third less than that of practical titanium-nickel SMAs. They believe that the alloy's low density could give it application in lightweight aerospace components, such as self-deployable space habitat frames and damping devises on spacecraft systems.

Mg-based SMAs could also be applied in the medical field, according to the researchers. Specifically, the Mg-Sc superelastic alloy could potentially be used in biodegradable, self-expandable stents to overcome restenosis—the recurrence of abnormal narrowing of an artery or valve after corrective surgery.

The researchers expect that in the future the alloy composition will be optimized to increase its operational temperature and potentially its biocompatibility and biodegradability characteristics.