J. Phys. IV France 112 (2003) 1047
Phonon precursors to the high temperature martensitic transformation in Ti 50Pd 42Cr 8S.M. Shapiro1, B.L. Winn1, D.L. Schlagel2, T.A. Lograsso2 and R.L. Erwin3
1 Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11973, U.S.A.
2 Ames Laboratory, Ames, IA 50011, U.S.A.
3 National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, U.S.A.
Inelastic neutron scattering measurements were carried out on the Ti 20Pd Cr alloy, which is a high temperature shape memory material. For , the transformation temperature is ~800K and for the composition studied ( at %) M K. The majority of the measurements were performed in the parent, B2-phase, up to 873K. Most of the phonons propagating along the three symmetry directions [ 00] , [ ] , and [ 0] were well defined with the exception of the [ 0] transverse acoustic mode with displacements along the [ - 0] corresponding to the ) etastic constant in the limit. These phonons are well defined for small , but for they are strongly overdamped near the transition temperature and become better defined at higher temperatures. An elastic peak develops in the cubic phase at and increases in intensity as M is approached. However, the dispersion curves show no anomaly at this particular wavevector, in marked contrast to the lattice dynamic studies of other systems exhibiting Martensitic transformations.
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