Structural and Phase Transformations and Physical and Mechanical Properties of Cu-Al-Ni Shape Memory Alloys Subjected to Severe Plastic Deformation and Annealing

Using the methods of electron microscopy and X-ray analysis in combination with measurements of the electrical resistance and magnetic susceptibility, the authors have obtained data on the peculiar features of pre-martensitic states and martensitic transformations, as well as subsequent decomposition, in the alloys with shape memory effect of Cu-14wt%Al-3wt%Ni and Cu-13.5wt%Al-3.5wt%Ni. For the first time, we established the microstructure, phase composition, mechanical properties, and microhardness of the alloys obtained in the nanocrystalline state as a result of severe plastic deformation under high pressure torsion and subsequent annealing. A crystallographic model of the martensite nucleation and the rearrangements beta(1)->beta(1)' and beta(1)->gamma(1)' are proposed based on the analysis of the observed tweed contrast and diffuse scattering in the austenite and the internal defects in the substructure of the martensite.

Automated summary

By using electron microscopy and X-ray analysis techniques, combined with measurements of electrical resistance and magnetic susceptibility, the authors have obtained data on the unique characteristics of pre-martensitic states and martensitic transformations, as well as subsequent decomposition in Cu-14wt%Al-3wt%Ni and Cu-13.5wt%Al-3.5wt%Ni shape memory effect alloys. The microstructure, phase composition, mechanical properties, and microhardness of nanocrystalline alloys produced by severe plastic deformation and subsequent annealing have been determined for the first time. A crystallographic model of martensite nucleation and rearrangements beta(1)->beta(1)' and beta(1)->gamma(1)' has been proposed based on analysis of observed tweed contrast and diffuse scattering in the austenite, as well as internal defects in the martensite substructure.