Measurement of deformation fields in polycrystalline OFHC copper

Validation of continuum crystal plasticity models for polycrystalline materials requires experiments with sub-grain scale resolution, performed on materials with realistically small grain sizes. To date only limited experiments have been performed to investigate displacement fields with resolution well below the grain scale over a wide field for polycrystals with realistic grain sizes. This paper explores high-resolution in-plane material stretch and rotation fields measured at the sub-grain scale for ensembles of 10–20 grains in 70 μm grain-size OFHC Cu. Using a novel photolithographic technique, a series of micron-scale grids were deposited onto the surface specimens that were subsequently subjected to compression or torsion to effective strains up to unity. The resulting grid patterns for compression exhibit a tendency toward localization of stretch and rotation fields, with larger grains less highly deformed. For the case of shear, there is a reduced tendency towards microstructural scale localization of the in-plane stretch and rotation fields.