Shape Memory Effect through L1₀-fcc Order-Disorder Transition

Abstract

Shape memory effect not associated with martensitic transformation but with order-disorder phase transformation is examined in the compounds of AuCu, CoPt and FePd. These exhibit the L1₀-fcc transition at 680K, 1060K and 950K, respectively, which is relatively high temperature. Under a uniaxial compressive stress, a reversible shape change (reduction and elongation in edge length) is observed by cooling and heating the specimen temperature. The elongation of the specimen associated with the disordering occurs at their equilibrium transition temperatures, and the reduction along the direction of a compressive stress associated with the ordering occurs at a certain supercooled temperature. A trial actuator constructed with FePd polycrystalline wire and a conventional inconel wire properly works by heating up and cooling down the temperature.