In order to study the microscopic mechanisms underlying the Martensitic Phase Transformations (MPT), Nuclear Magnetic Resonance (NMR) experiments have been performed in Ni - Ti shape memory alloys. Ni - Тi alloys and especially thin films are of great technological interest as material basis for actuators and smart micro-systems. NMR measurements in Ni - Ti are very difficult to achieve because of the low NMR sensitivity of <^>61Ni and <^>47,49Ti nuclei and their substantial quadrupole moments. However we have demonstrated that such experiments were possible even in non-enriched samples when a strong magnetic field (14T) is applied. Systematic measurements of the spectral linewidths and Knight shifts as a function of temperature has been performed in Тi - 50,6 at. % Ni wires and sputter deposited thin films displaying a two-steps transformation via R-phase. The volume fraction of the different phases present at a given temperature could be obtained by spectral deconvolution. The growth curve of martensite as obtained by NMR provides quantitative information that cannot be detected by other experimental techniques. As a matter of fact it is shown that in both samples the transformation is not complete even at a temperature well below Mf as determined by Differential Scanning Calorimetry.

Індекс рубрикатора НБУВ: К232.204.3

Рубрики:

Структурні та фазові перетворення у нікелі та його сплавах

Шифр НБУВ: Ж14161 Пошук видання у каталогах НБУВ 

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