Two internal friction peaks associated with martensitic and I/C ( R ) phase transformations were observed in the first thermal cycle for NITi alloy. By utilyzing the experimental data of IF (as a function of [MATH]/w, an explicit functional relationship of interface dynamics was obtained as V=V*exp(-ƊG*/ƊG-ƊGR), and the expression of IF during the process of transformation as Q-1=C-ƊG*(dF/dT)µ[MATH]/w(ƊG-ƊGR)2, where V is the average velocity of phase interface, ƊG is the phase transformation driving force ; and ƊGR is the transformation resistant force, which has the order of 5 cal/mol, 8cal/mol and 10 cal/mol for I/R, R/M and M/p transformations respectively. The "Soft Mode Effect" during the transformation processes has been discussed
The Martensitic (MP) and incommensurate/commensurate (I/C) phase transformations during the athermal process of NiTi alloy were studied by the measurements of internal friction, elastic modulus and electric resistance simultaneously. The IF behaviour in the processes of MP and I/C phase transformations are nearly the same and is associated with the motion of phase interface under the action of phase transformation driving force. Starting with the interface dynamics model, the interface dynamic behaviour of MP and I/C transformations were . studied. An explicit functional relationship of the interface dynamics in the process of marten-sitic transformation was obtained as V = V* exp(-△G*/△G - △GR) and the expression for IF during the process of phase transformation as Q-1 = (n2/2)×(μ△G*/(△G-△GR)2) dF/dT·T/ω. The transformation resistance froce △GR is the order of 10 cal/mol. The "soft mode effect" during the transformation process was discussed, and it was shown that the softfening of pho-non mode and the modulus defect associated with interface motion coexist in the processes of martensitic and I/G phase transformations.
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