J. Phys. IV France 11 (2001) Pr8-95-Pr8-100
Nucleation of R-phase as studied by dynamic Young's modulus in the Ni49Ti51, aged alloyB. Coluzzi, A. Biscarini, R. Campanella, G. Mazzolai and F.M. Mazzolai
INFM-UDR of Perugia, Physics Department, University of Perugia, Via A. Pascoli 5, 06100 Perugia, Italy
The Young's modulus E and the internal friction Q-1 have been measured during thermal cycles carried out at temperatures higher than the start temperature Rs (Rs = 335 K) of the B2 → R martensitic transition in the Ni49Ti51 alloy, prior cold-worked (ε = 32 %) and then aged at 673 K for 30 minutes. The cooling/heating E(T) and Q-1(T) branches of cycles extending down to the temperatures 350, 340 and 336 K exhibit progressively increasing thermal hysteresis, while those referring to a cycle only extending down to 369 K does not. This thermal hysteresis is attributed to the formation of stable nuclei of R martensite at dislocation or at some other type of lattice defects.
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