Metastable effects on martensitic transformation in SMA

Abstract

The Clausius-Clapeyron coefficient (CCC or αcc) or relation of the stress to transform a thermoelastic SMA sample and temperature, is revisited for 1-dimensional stressed SMA when polycrystalline materials are used. The experimental method is discussed in the frame of equilibrium thermodynamics for polycrystalline materials. Suggestions for evaluation of the experimental value in polycrystalline NiTi and CuAlBe specimens are proposed. The analysis for NiTi wire gives a CCC ofαcc=6.3±0.3 MPa K -1 . On the other hand CuAlBe provides a value of αcc=2.2±0.4 MPa K -1 for tensile stress.