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A lightweight shape-memory magnesium alloy

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Science  22 Jul 2016:
Vol. 353, Issue 6297, pp. 368-370
DOI: 10.1126/science.aaf6524

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Lightweight shapeshifting alloys

Shape memory alloys (SMAs) spring back into shape after they are deformed, a useful property for a variety of applications. Transition metal alloys, which are robust but dense, dominate the SMA landscape. Ogawa et al. report a new type of lightweight SMA made from magnesium and scandium, which has comparable properties to known SMAs but at significantly lower density. Although this magnesium-scandium alloy is limited to low-temperature applications, development of a new lightweight class of SMAs could be on the horizon.

Science, this issue p. 368

Abstract

Shape-memory alloys (SMAs), which display shape recovery upon heating, as well as superelasticity, offer many technological advantages in various applications. Those distinctive behaviors have been observed in many polycrystalline alloy systems such as nickel titantium (TiNi)–, copper-, iron-, nickel-, cobalt-, and Ti-based alloys but not in lightweight alloys such as magnesium (Mg) and aluminum alloys. Here we present a Mg SMA showing superelasticity of 4.4% at –150°C and shape recovery upon heating. The shape-memory properties are caused by reversible martensitic transformation. This Mg alloy includes lightweight scandium, and its density is about 2 grams per cubic centimeter, which is one-third less than that of practical TiNi SMAs. This finding raises the potential for development and application of lightweight SMAs across a number of industries.

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