Motion of dislocations and interfaces during deformation of martensitic Cu-Al-Ni crystals

Investigations of the ultrasonic strain amplitude-dependent internal fricti on (ADIF) and of the influence of ultrasonic vibrations on the macroplastic strain (the acoustoplastic effect) have been performed in situ during defo rmation of quenched Cu-Al-Ni single crystals in the Pi martensitic phase. T he effect of the macroscopic plastic strain rate on the ADIF and acoustopla stic effect as well as the kinetics of the acoustoplastic effect has been s tudied. The results of in situ ADIF measurements are compared with data on the ADIF temperature dependence. Observed regularities are attributed to di fferences in the mechanisms of the macroplastic deformation of the martensi tic phase, related to the motion of intervariant interfaces, and of the rev ersible anelastic strain, which, at ultrasonic frequencies and moderate str ain amplitudes, is largely due to the oscillatory motion of the partial dis iocations. The conclusion has been drawn that the dynamics of partial dislo cations at temperatures of 210-300 K is to a great extent determined by the ir interaction with atmospheres of mobile pinners with saturated density. S imultaneous measurements of the ADIF and acoustoplastic effect allows the c onclusion that, for high oscillatory strain amplitudes, the breakthrough of partial dislocations beyond the mobile atmospheres of pinners initiates th e step-like accumulation of the macroplastic strain due to the motion of in tervariant boundaries. (C) 2000 Acta Metallurgica Inc. Published by Elsevie r Science Ltd. All rights reserved.