Deformation mechanisms underlying tension–compression asymmetry in magnesium alloy ZK60 revealed by acoustic emission monitoring

Evolution of Mechanical Twinning during Cyclic Deformation of Mg-Zn-Ca Alloys

“…The AE energy also drops at the point of loading reversal and remains low as long as the de-twinning process is active on the tensile part of each cycle. This finding is close to the results reported in [32,54,59], where it was argued that the de-twinning process, which is systematically observed at strain path reversal in Mg polycrystals, proceeds at the velocities much slower than those at twin nucleation and is not directly detectable by AE. This can be clearly seen on the enlarged fragment of the AE time-series shown in Figure 5b.…”

“…This task is challenging yet tractable, since different AE sources generate different waveforms and therefore different Fourier power spectra at the sensor output. Applying the same ASK algorithm with a sliding window to the raw data acquired during cyclic deformation and grouping the frames with similar spectral features, allowed us to identify the signals corresponding to twinning in a way similar to that reported previously [32,54]. Figure 7 shows the results of the cluster analysis represented as the cumulative AE energy (a); and the average AE energy per cycle (b) separated for tensile and compressive stages.…”

“…The behavior of the median frequency, which is shown in Figures 4 and 5, is similar for both specimens and is specific for deformation mechanisms operative in Mg. The details of the particular features of the fm evolution in response to dislocation slip and twinning have been highlighted in [32] (cf. also [54,56]).…”

“…The fm value drops at the point of reversal of the loading direction, and then it starts rising again as deformation proceeds beyond a certain stress, which can be associated with a "true" yield stress and which reasonably increases as The behavior of the median frequency, which is shown in Figures 4 and 5, is similar for both specimens and is specific for deformation mechanisms operative in Mg. The details of the particular features of the f m evolution in response to dislocation slip and twinning have been highlighted in [32] (cf. also [54,56]).…”

Fatigue Performance of Mg-Zn-Zr Alloy Processed by Hot Severe Plastic Deformation

“…The main reason for that is apparently related to the texture which is much weaker in both studied alloy conditions than that in the conventional extruded Mg alloys. Notwithstanding, the effect of texture and the interplay between the dislocation slip and twinning cannot be completely eliminated even in weakly textured Mg alloys [29]. As a result, some tensile mean stress arises in both alloy types.…”