Effect of solute clusters on plastic instability in magnesium alloys


The interaction between solute atoms and matrix dislocations during plastic deformation of materials strongly influences the flow behavior and can lead to plastic instability at the macroscopic scale. In this study, Lüders band formation and dynamic strain aging phenomena were investigated in a Mg–1%Mn-1%Nd (wt.%) alloy, deformed in uniaxial tension at ambient temperature and 150 °C. The investigated alloy was studied in the initial as-extruded state and after a subsequent heat treatment at 275 °C for 120 min, which allowed for a variation of solute concentration in the microstructure, and thus for a different type/level of solute – dislocation interaction. Microstructure investigations at near-atomic resolution using three dimensional atom probe tomography were carried out in order to visualize the spatial distribution of alloying elements and reveal potential solute clustering trends in connection with the occurrence of plastic instability. Identified nanoscale solute clusters were analyzed on the basis of their size distribution, chemical composition, and statistical significance. Results demonstrate that the number, as well as the types of solute clusters, play an essential role in triggering plastic instability by interacting with deformation carriers at the atomic scale.
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