Thermo-Deformation Behavior of Functional Shape-Memory Copper- and Iron-Based Alloys

The alloys undergoing martensitic transformation can demonstrate a number of unusual functional properties, namely, shape memory effect, superelasticity, plasticity of transformations, generate significant reactive stresses, etc. The most attractive among the materials of this class in terms of their practical application are copper- and iron-based alloys in which multi-stage phase transformations in external loading field are revealed. Polycrystalline Cu-Al-Mn and Fe-Ni-Co-Ti-Cu alloys of different composition have been chosen for the investigation. Characteristic temperatures of matrensitic transformation, coefficients of thermal expansion of high- and low-temperature phases, as well as volume effect of transformation were determined against the alloy composition and heat treatment.

The complex phase diagrams of deformation behavior have been plotted for Cu-Al-Mn and Fe-Ni-Co-Ti-Cu alloys under the influence of: a) fixed temperature at various loading conditions; b) fixed loading at various temperatures; c) simultaneous action of external force and temperature field. The studied alloys are promising materials for their practical application as functional strain sensors in a wide thermo-power range of use.