No abstract

Effect of the loading mode on the evolution of the deformation mechanisms in randomly textured magnesium polycrystals − comparison of experimental and modeling results, International Journal of Plasticity (2015),

Various dynamical systems with many degrees of freedom display avalanche dynamics, which is characterized by scale invariance reflected in power-law statistics. The superposition of avalanche processes in real systems driven at a finite velocity may influence the experimental determination of the underlying power law. The present paper reports results of an investigation of this effect using the example of acoustic emission (AE) accompanying plastic deformation of crystals. Indeed, recent studies of AE did not only prove that the dynamics of crystal defects obeys power-law statistics, but also led to a hypothesis of universality of the scaling law. We examine the sensitivity of the apparent statistics of AE to the parameters applied to individualize AE events. Two different alloys, MgZr and AlMg, both displaying strong AE but characterized by different plasticity mechanisms, are investigated. It is shown that the power-law indices display a good robustness in wide ranges of parameters even in the conditions leading to very strong superposition of AE events, although some deviations from the persistent values are also detected. The totality of the results confirms the scale-invariant character of deformation processes on the scale relevant to AE, but uncovers essential differences between the power-law exponents found for two kinds of alloys.

No abstract

No abstract

No abstract

No abstract

The effect of the orientation of the non-recrystallized grains (non-DRX) and the LPSO phase on plasticity in extruded Mg97Y2Zn1 alloy with a bimodal grain structure have been studied in-situ using the combination of synchrotron diffraction and acoustic emission techniques during compression tests. The adaptive sequential k-means (ASK) procedure was applied to analyze the acoustic emission signal. This method can successful separate the signal for each possible deformation systems. Combining both techniques the deformation mechanisms that take place during the compression tests under different loading directions have been distinguish. Independently of the loading direction, the beginning of the macroscopic plasticity is always controlled by the activation of basal slip system in the DRX grains. However, highly oriented non-DRX grains and LPSO phase have a strong influence over the compressive deformation of the MgY2Zn1 alloy. The basal planes in the non-DRX grains were oriented parallel to the extrusion direction (ED). Thus, the activation of the extension twinning was found to be significant only in the ED mode. In the other two loading cases, TD and 45, the activation of non-basal slip systems has been detected. On the other hand, the reinforcing effect of the   1012 1011 2 elongated LPSO phase is the most effective, if the loading axis is aligned with the fiber direction (extrusion direction) since the load transfer mechanism is more effective. In this loading case, the LPSO can be plastically deformed due to kinking. This deformation mode has been isolated by the ASK procedure and characterized by in-situ scanning electron microscopy.