NiTi Shape Memory Marformed Alloy Studied by Electron Beam Precession TEM Orientation Mapping Method
P. Świec, M. Zubko, Z. Lekston and D. Stróż
Institute of Material Science, University of Silesia, 75 Pułku Piechoty 1a, 41-500 Chorzów, Poland
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Severe plastic deformation by cold-rolling in martensitic state was applied to Ni50.4Ti49.6 shape memory alloy. Received materials with 17, 20, 25, and 35% deformation were further annealed at 450°C for 15 min. After such treatment hardness of this alloy increased significantly reaching 365 HV0.5 for highest deformation degree. Calorimetric studies revealed two-stage and two-step character of martensitic transformation occurring in all specimens. Nanocrystalline structure with average grain size 53, 34, 28, and 24 nm was obtained. In material with 35% of deformation amorphous regions containing a nuclei of B2 parental phase with average size of 5 nm were observed. To determine the crystallographic orientation of observed nanograins and for better phase analysis, electron beam precession transmission electron microscopy orientation mapping was performed.

DOI: 10.12693/APhysPolA.131.1307
PACS numbers: 62.20.fg, 62.20.F-, 61.43.Dq, 61.66.Bi, 68.37.Ef, 62.25.-g, 64.70.Nd