Abstract
Shear forcing, a novel solid state material processing technique, helps avoid melt processing and can result in highly refined microstructures not achievable by conventional methods. In order to develop such shear-based solid phase processing methods for metallic alloys, we aim to better understand the fundamental atomic scale mechanisms of mass and energy transfer in materials under shear deformation. To achieve this aim, we employed synchrotron-based in situ and ex situ high-energy x-ray diffraction capabilities under high pressure, with or without shear deformation, using a diamond anvil cell, as well as the FlexiStir in-situ friction stir and processing system. The obtained synchrotron-based XRD results were correlated with detailed microstructural characterization before and after shear deformation using transmission electron microscopy and atom probe tomography, to develop a comprehensive understanding of the structural and compositional changes in the microstructure due to the shear deformation. Our results on structural and chemical modifications of several model metallic alloys such as Al-Si, Cu-Nb and Cu-Ni provide new insights on the unique role of shear deformation in formation of metastable states, as well as in modifying the phase transformation pathways of these alloy systems. These new insights will be presented, highlighting the potential of using shear forcing for processing metallic alloys to achieve unique microstructural features which in turn may offer unique mechanical properties.
