Jerky flow in dilute alloys, or the Portevin-Le Chatelier effect, is investigated using statistical analysis of time series characterizing the evolution of the plastic activity at distinct scales of observation, namely, the macroscopic scale of stress serrations and a mesoscopic scale pertaining to the accompanying acoustic emission. Whereas the stress serrations display various types of statistical distributions depending on the driving strain rate, including power-law, peaked and bimodal histograms, it is found that acoustic emission is characterized by power-law statistics of event size in all experimental conditions. The latter reflect intermittency and self-organization of plastic activity at a mesoscopic scale. This shift in the observed dynamics when the observation length scale is decreased is discussed in terms of the synchronization of small-scale events.

The earlier high-pressure stndy of Cw concenmted on the orientational transition and mom-temperature transformations observed in diamond anvils. This work presents a parl of the T-P phase diagram for solid Cw at pressures up to 20 kbar in the temperahlre range extended to 700 K. A new phase region is outlined herein. The new phase is retained to ambient conditions and preliminarily characterized. The new phase is more dense than the initial Cm by al least 8.5% and less compressible by -1.5 times. Its crystal svucmre is very different from the well known face-centred cubic and simple cubic phases, and its recovely to a cubic phase is associated with an endothermal heat effect of -23 I g-', The nature and the lhemcdynamic stability of the new phase are discussed in connection with polymerization of & molecules, which seem likely.

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The paper presents a new approach to the nature of heat effects and shear modulus softening in metallic glasses. The approach is based on the assumption that the glass contains quenched-in “defects”—elastic dipoles. Using the nonlinear elastic representation of the internal energy of glass with quenched-in elastic dipoles, we derive a simple analytical law, which connects the heat flow and temperature derivative of the shear modulus. Specially performed experiments confirmed the validity of this law. The exothermal and endothermal heat processes in glass reveal through the relaxation of the shear modulus confirming it as a key parameter for the understanding the relaxation processes in glasses.

The work is devoted to a brief overview of the Interstitialcy Theory (IT) as applied to different relaxation phenomena occurring in metallic glasses upon structural relaxation and crystallization. The basic hypotheses of the IT and their experimental verification are shortly considered. The main focus is given on the interpretation of recent experiments on the heat effects, volume changes and their link with the shear modulus relaxation. The issues related to the development of the IT and its relationship with other models on defects in metallic glasses are discussed.