Triple Junction Segregation Dominates the Stability of Nanocrystalline Alloys.

We present large-scale atomistic simulations that reveal triple junction (TJ) segregation in Pt-Au nanocrystalline alloys in agreement with experimental observations. While existing studies suggest grain boundary solute segregation as a route to thermally stabilize nanocrystalline materials with respect to grain coarsening, here we quantitatively show that it is specifically the segregation to TJs that dominates the observed stability of these alloys. Our results reveal that doping the TJs renders them immobile, thereby locking the grain boundary network and hindering its evolution.

Atomistic and machine learning studies of solute segregation in metastable grain boundaries.

The interaction of alloying elements with grain boundaries (GBs) influences many phenomena, such as microstructural evolution and transport. While GB solute segregation has been the subject of active research in recent years, most studies focus on ground-state GB structures, i.e.

Grain Boundary Solute Drag Model in Regular Solution Alloys.

We present a grain boundary (GB) solute drag model in regular solution alloys. The model accounts for solute-solute interactions in both the bulk and GBs and captures effects such as monolayer, multilayer, and asymmetrical segregation. Our analysis shows that deviations from ideal solution thermodynamics play a paramount role, in which solute drag is shown to scale with solute-solute interaction parameters.

The role of grain boundary character in solute segregation and thermal stability of nanocrystalline Pt-Au.

Nanocrystalline (NC) metals suffer from an intrinsic thermal instability; their crystalline grains undergo rapid coarsening during processing treatments or under service conditions. Grain boundary (GB) solute segregation has been proposed to mitigate grain growth and thermally stabilize the grain structures of NC metals. However, the role of GB character in solute segregation and thermal stability of NC metals remains poorly understood.

Tensile deformation behavior of twist grain boundaries in CoCrFeMnNi high entropy alloy bicrystals.

High entropy alloys (HEA) are a class of materials that consist of multiple elemental species in similar concentrations. The use of elements in far from dilute concentrations introduces a multi-dimensional composition design space by which the properties of metallic systems can be tailored. While the mechanical behavior of HEAs has been the subject of active research recently, the role of grain boundaries (GBs) in their deformation behavior remains poorly understood.

Continuum modeling of bulk metallic glasses and composites.

At low temperatures, monolithic bulk metallic glasses (BMGs) exhibit high strength and large elasticity limits. On the other hand, BMGs lack overall ductility due to highly localized deformation mechanisms. Recent experimental findings suggest that the problem of catastrophic failure by shear band propagation in BMGs can be mitigated by tailoring microstructural features at different length scales to promote more homogeneous plastic deformation.