| Issue |
J. Phys. Colloques
Volume 42, Number C5, Octobre 1981
ICIFUAS-7Seventh International Conference on Internal Friction and Ultrasonic Attenuation in Solids |
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|---|---|---|
| Page(s) | C5-1037 - C5-1042 | |
| DOI | https://doi.org/10.1051/jphyscol:19815160 | |
Seventh International Conference on Internal Friction and Ultrasonic Attenuation in Solids
J. Phys. Colloques 42 (1981) C5-1037-C5-1042
DOI: 10.1051/jphyscol:19815160
THE INTERNAL FRICTION SPECTRUM OF PREMARTENSITIC TRANSFORMATIONS
O. Mercier1, B. Tirbonod2 et E. Török31 Brown Boveri Research Centre, 5400 Baden, Switzerland
2 Nuclear Engineering Laboratory, Swiss Federal Institute of Technology, 1007 Lausanne, Switzerland
3 Institut Straumann, 4437 Waldenburg, Switzerland
Abstract
In equiatomic NiTi, two internal friction peaks can appear during the transformation to the martensitic phase. One of the two peaks, which is associated with a sharp minimum of the Youngs's modulus, is explained as resulting from a premartensitic phase transition, which occurs in two stages : a second order phase transition, associated with a softening of the (110) transverse phonon mode, followed by the "lock in" of this incommensurate phase. The other peak is associated with the martensitic transformation itself. Experiments have been done for several NiTi base alloys and have shown that the second order phase transition occurs in all alloys, in which Ni is subtituted by Cu or Fe, whereas the "lock in" phase transition is only observed for alloys having additions of Fe. It is also shown that the CuZnAl and the CuAlNi alloys do not show a similar behaviour.