THE INTERNAL FRICTION STUDY OF INTERFACE DYNAMICS OF NiTi ALLOY IN THE PROCESSES OF MARTENSITIC AND I/C PHASE TRANSFORMATION

Abstract
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-ƊG_R), and the expression of IF during the process of transformation as Q^-1=C-ƊG*(dF/dT)µ[MATH]/w(ƊG-ƊG_R)², where V is the average velocity of phase interface, ƊG is the phase transformation driving force ; and ƊG_R 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.