Effect of Grain Boundary Segregation On M H. Somekawa and Alok Singh Research Center for Structural Materials, National Institute for Materials Science (NIMS) Magnesium (Mg) and its alloys have attracted immense attention, because of being the lightest among common metallic materials. However, the magnitude of application of these alloys is still very limited due to low ductility and poor formability at ambient temperature, associated with the hexagonal crystal structure. As in case of other metallic materials, control of microstructure and alloying are the well-known strategy to overcome such intrinsic issues. Particularly, grain refinement is one of the effective methods for improving mechanical properties, e.g., ductility and toughness, and secondary formability. Thermomechanical process is generally used to control the microstructure in metallic materials. It is noted that alloying elements are segregated at grain boundaries during these processes, which affect mechanical properties and deformation mechanisms. Nevertheless, there are no systematic studies on this aspect on Mg alloys. Therefore, in this study, we have examined the impact of solute atoms segregation at grain boundaries on mechanical properties using fine-grained Mg binary alloys. Alloying elements are confirmed to be segregated at grain boundaries, irrespective of the type of solute element. The mechanical properties are changed by grain boundary segregation; especially, segregation of Mn to grain boundaries leads to enhancing ductility due to grain boundary sliding. Effect of Yttrium Addition on the Nanoindentation Behavior at Boundaries V. Paul 1, H. Somekawa 1 and T. Ohmura 1 1 Research Center for Structural Materials, National Institute for Materials Science (NIMS) The effect of Y addition in Mg–Y alloy on the local mechanical behavior was investigated via the nanoindentation technique to reveal diffusive and displacive phenomena near the grain boundary. Both creep and constant strain rate tests were performed on the Mg–Y alloy, and the data points on the flow stress vs. effective strain rate plot align linearly across a significantly wide range spanning six orders of magnitude in strain rate. Additionally, the strain-rate sensitivities of the grain interior and boundary in the Mg–Y alloy were similar, suggesting a consistent plasticity even at the grain boundary. Physical hardness (α), which is derived from the slope of the P/h–h curve (P and h represent load and displacement, respectively), was analyzed to determine the plastic deformation resistance at the grain boundary. According to the results, there is no remarkable plasticity resistance by the grain boundary. Based on these findings, it is presumed that the addition of Y stabilized the grain boundary to reduce the diffusivity and enhance the activation of the non-basal slip system in a displacive behavior, leading to suppression of the grain boundary effect in the Mg alloy. 46PP22--0055 PP22--0066 Poster Presentation ｜NIMS Award Symposium 2023 P2 ｜ Characterizationechanical Properties in Mg Alloys Mg–Y Alloy Grain
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