Time-resolved and in-situ Observation of Semisolid Deformation in Al–Cu Alloys with Equiaxed and Columnar Grain Structures by Using a Combination Technique of 4D-CT and 3DXRD

摘要

Time-resolved combined absorption tomography and three-dimensional X-ray diffraction was developed to study semisolid deformation of metallic alloys, which combined time-resolved tomography and three-dimensional X-ray diffraction microscopy (3DXRD). The combined technique allowed observation of configuration and crystallographic orientation of solid grains, whereby translation and rotation of solid grains induced by interaction between solid grains during semisolid deformation was analyzed. During the compression tests of a semisolid Al–10mass%Cu alloy with the equiaxed grain structure, translation and rotation of solid grains rather than the plastic deformation played a dominant role in the deformation until strain reached ?0.04. In a portion of the specimen, a gap between solid grains expanded owing to the interaction between solid grains, and consequently apparent volume expansion (dilatancy ) occurred. The solid grains around the expanded region possessed similar rotational axis directions, which were perpendicular to the normal direction of the expanded region. As the compression proceeded, both translation/rotation and the plastic deformation of solid grains occurred owing to an increase in physical contact between solid grains. For a semisolid Al–10mass%Cu alloy with the columnar grain structure, solid grain comprised a single crystallographic domain. Inflection of the dendrite arms was confirmed by 3DXRD, where the compression of strain at ?0.25 caused the grain to be inflected up to 12 degrees. The strain distribution in the grain was estimated using the inflection angle. In-situ observation revealed that the behaviors of solid grains and the liquid phase in semisolid alloys during the compression tests differed according to the structure.