Deformation Induced Complexion Transitions in Nanocrystalline Alloys

TL;DR

This study investigates how plastic deformation induces complexions transitions in nanocrystalline Pd-Au alloys, revealing stress-driven changes in grain boundary enthalpy that suggest a continuous, non-equilibrium complexion transition.

Contribution

It provides the first combined atomistic simulation and calorimetry evidence of deformation-induced complexion transitions in nanocrystalline alloys.

Findings

Plastic deformation increases grain boundary enthalpy.

Stress induces a transition from low-energy to high-energy GB states.

GBs store deformation history through configurational changes.

Abstract

Grain boundary (GB) enthalpies in nanocrystalline (NC) $\mathrm {Pd_{90}Au_{10}}$ are studied after preparation, thermal relaxation and plastic deformation. By comparing results from atomistic computer simulations and calorimetry, we show that increasing plastic deformation of equilibrated NC $\mathrm {Pd_{90}Au_{10}}$ specimen causes an increase of the stored GB enthalpy $\Delta \gamma$. We interpret this change of $\Delta \gamma$ as stress-induced complexion transition from a low-energy to a high-energy GB-core state. In fact, GBs behave not only as mere sinks and sources of zero- and one-dimensional defects or act as migration barriers to the latter but also have the capability of storing deformation history through configurational changes of their core structure and hence GB enthalpy. Such a scenario can be understood as a continuous complexion transition under non-equilibrium conditions, which is related to hysteresis effects under loading-unloading conditions.