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Dynamics of the deformation band formation during creep in an Al-Mg alloy was investigated by simultaneous high-speed video recording of deformation bands with an extremely high time resolution of 40 µs and measurement of the concomitant acoustic emission. The results are consistent with the mechanism where the trigger of a strain step on the creep curve is the nucleation and rapid widening of a primary deformation band, generating an acoustic emission signal within one millisecond. Correlations between various stages of the deformation band formation, acoustic emission, and stress response are explored in detail. Notably, the stress drop rate and the amplitude of the acoustic emission signal are found to be linearly related. The mechanism of the acoustic emission associated with the initial rapid stage of the band development is discussed.

The dynamics of macrolocalized deformation bands generated by the impact of a Vickers indenter on the surface of an AlMg6 aluminum-magnesium alloy deformed under creep conditions was studied by high-speed video recording and acoustic emission methods. It has been established that these bands are the trigger for the development of a macroscopic jump in plastic deformation on the creep curve. It is shown that in alloys exhibiting the Portevin-Le Chatelier effect it is necessary to take into account the initiation and propagation of deformation macrobands during surface erosion damage and to estimate the volume and morphology of the plastic zone during impact microindentation of a deformable alloy. Keywords: intermittent deformation, deformation band, impact, indenter, aluminum-magnesium alloy.

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