Postavalanche Relaxation Sheds Light on Twinning Mechanisms

Avalanches are abundant abrupt events that occur during various physical processes, where the material transitions between equilibrium states through complex dynamics. Relaxation's dynamics are simpler and milder compared to avalanches, typically following a well-defined kinetic law. Here, we reveal the elemental differences between avalanches and relaxations during deformation twinning in magnesium in terms of their rate and duration. At the same time, we find that each avalanche is followed by relaxation with an almost identical magnitude. An avalanche occurs at the μs timescale and corresponds to a twin nucleation while relaxation occurs at the ms timescale and corresponds to twin growth. Our results indicate that the local volumes twinned during these two coupled processes are nearly identical. This implies a simple geometrical relation between twin nucleation and subsequent twin growth, shedding light on the basic mechanisms during the early stages of twinning.