Characterization of a Ni 50Ti 50 shape memory strip produced by twin roll casting technique

Abstract

An NiTi alloy was produced by twin roll casting technique. Microstructure, thermal behaviour, texture and shape recovery were studied by optical microscopy, differential scanning calorimetry (DSC), X-ray diffraction and elongation measurements. The strip reveals a relatively large thermal hysteresis loop (almost 70°), which is characteristic for the martensitic transformation course B2 ↔ B19′. The crystallization front which simultaneously proceeds from the outer part of the strip to its centre causes a preferential orientation of the growing grains. In consequence, a texture is formed as a mixture of the fibre 〈0 0 1〉 orientation and the sheet texture component {0 0 1}〈1 0 0〉. The strip shows a good shape recovery with the recoverable elongation of 3.5%.