Shape memory alloy-based composites fabricated by severe plastic deformation.

F.M. Braz Fernandesa, E. Camachoa, C. Marcua,b, N. Schellc, C. Guraub, G. Guraub

aCENIMAT / I3N - Departamento Ciência dos Materiais, Universidade Nova de Lisboa / FCT, 2829-516 Caparica, Portugal

bFaculty of Engineering, “Dunărea de Jos” University of Galati, Galaţi, 800201, Romania

cHigh Energy Materials Science, PETRA-III, DESY, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max Planck-Str. 1,21502, Geesthacht, Germany

High-Speed High Pressure Torsion (HS-HPT) has been used to promote severe plastic deformation of Ni-rich and Ti-rich Ni-Ti shape memory alloys, fabricating multiple layered structures (up to 32 layers), embedding other metallic alloys, such as Mg alloy. The phases present at room temperature were identified by synchrotron radiation based X-ray diffraction. The transformation characteristics were determined by Differential Scanning Calorimetry (DSC) using a series of thermal cycles comprising 2 heating ramps up to 500ºC intercalated by 3 conventional cooling / heating cycles between +150 and -150 ºC in order to assess the relevance of recrystallization and precipitation phenomena.

Fig. 1. HS-HPT machine and active part of HS-HPT machine

Fig. 2. Strategy for the multilayer processing.

Fig. 3. Thermal cycle used for DSC tests.