Synchronised in-situ X-ray diffraction and strain measurement during deformation of nanocrystalline PdAuWednesday (26.09.2018) 15:00 - 15:15 S1/01 - A3 Part of:
Scaling the grain size of PdAu down to the low end of the nano scale (approximately 10nm) entails a dramatic change in mechanical properties (e.g. increased yield strength, tension-compression asymmetry, high strain rate and temperature sensitivity, lowered ductility).
In a recent study, Grewer et al.  examined the deformation of nanocrystalline PdAu in an in-situ experiment using a combination of optical strain and synchrotron-based X-ray diffraction measurement. The central result was a quantitative estimate of the contributions of elasticity, stress driven grain boundary migration and dislocation glide to the overall deformation.
In continuation of this work, we explored the effects of different strain rates and stress states, respectively, by a series of experiments at beamline ID11 at the ESRF. Scattering data with a high temporal resolution provide us with detailed information on the evolving stress state in the crystalline phase, while we obtained the macroscopic stress-strain evolution from simultaneously recorded displacement and force measurement. By juxtaposing informations on the total stress/strain and the crystalline share, we study how the ensemble of nanocrystallites interacts with the embedding grain boundary phase. Based on that, we investigate possible origins of strain rate sensitivity or tension-compression asymmetry.
 M. Grewer et al., Anatomizing deformation mechanisms in nanocrystalline Pd90Au10, Mechanics of Materials, 114, 2017, 254-267