Author:

Keywords:

copper alloys, martensitic transformations, stabilization, plastic deformation, shape-memory alloys, reverse transformation, beta'(1) martensite, single-crystals, niti, 0910 Manufacturing Engineering, 0912 Materials Engineering, 0913 Mechanical Engineering, Materials

Abstract:

Cu-AI-Be beta'(1) martensite exhibits different levels of stabilization after various heat treatments (direct quenching into martensite, step-quenching, air cooling). However, this stabilization does not demonstrate time dependence upon martensite ageing at around room temperature, and can be considered as instantaneous. Cu-Al-Be martensite also stabilizes as a result of deformation of martensite starting from rather low values of prestrain. The conclusion is drawn that Cu-Al-Be alloy exhibits purely "mechanical" stabilization both after heat treatments and upon plastic deformation due to jamming the motion of interfaces. Non-elastic accommodation of transformation strain under a combined action of transformation stress and residual thermal stresses during the first direct martensitic transformation (MT), and "kinetic" stabilization due to sweeping-up of quenched-in defects during the martensitic transformation are considered as possible mechanisms of the observed instantaneous stabilization registered after heat treatment. (C) 2003 Published by Elsevier B.V.