[2019-4-22]Lecture Prof. Andy Godfrey, In-situ investigations of plastic yielding in the near-micrometer grain size regime of aluminum prepared by spark-plasma sintering
Lecture: In-situ investigations of plastic yielding in the near-micrometer grain size regime of aluminum prepared by spark-plasma sintering
Speaker：Prof. Andy Godfrey
Time: 10:00 am, Apr. 23th, 2019
Location: 210 meeting room, MSE building
Abstract：By control of the sintering conditions and powder characteristics is it possible to prepare microstructures of in a fully recrystallized state with controlled grain size using spark plasma sintering. This has been used to investigate the effect on mechanical properties of grain size heterogeneity specifically in the near-micrometer regime in samples of aluminum by careful mixing of powders. A detailed microstructural characterization of the as-synthesized samples been carried out using electron backscatter diffraction, transmission electron microscopy and high-energy X-ray diffraction. Investigation of deformed samples shows several transitions in dislocation patterning with decreasing length scale, and reveals a limit in grain subdivision by formation of dislocation rotation boundaries. As part of ongoing work to understand the onset of plastic flow in these samples in-situ deformation experiments have been also carried out using high energy synchrotron radiation, supplemented by in-situ studies in the scanning electron microscope using digital image correlation. The results of these two techniques offer different perspectives on the plastic yielding and the elastic-plastic transition in metals with a near-micrometer grain size. Examples will also be given of the use of spark plasma sintering to synthesize model two-phase systems, where the volume fractions, average size and strength of each component can be varied independently.
