Abstract: The influence of heat treatment on the microstructure and the microtexture of electrodeposited Ni and Ni-Co layers was investigated with Electron Backscatter Diffraction (EBSD) with high resolution. Samples were annealed for 1 hour at 523 K and 673 K, the temperature region wherein recrystallisation occurs. The results are discussed in relation to the resolution of EBSD for the very fine grained electrodeposits and previous X-ray diffraction investigations.
Abstract: Laser-Ultrasonics (LUS) provides a means of obtaining microstructure information
continuously and non-destructively both in the laboratory and for quality control on-line in industry. Ultrasound is both generated and recorded using lasers which permits remote, non-contact operation with fast sampling and also the capability of working at high temperatures or at moving surfaces, for example during industrial continuous annealing. Examples of dynamic heating trials will be presented for samples of cold rolled steel sheets where primary recrystallisation and ferrite austenite transformation are monitored in-situ as a function of temperature. Examples are also presented where the grain size of low carbon steels have been quantitatively analysed and show very good agreement with microscopy methods.
Abstract: 3-Dimensional X-Ray Diffraction (3DXRD) microscopy is a tool for fast and non-destructive characterization of the individual grains, sub-grains and domains inside bulk materials. The method is based on diffraction with highly penetrating hard x-rays, enabling 3D studies of millimeter - centimeter thick specimens. The position,
volume, orientation, elastic and plastic strain can be derived for hundreds of grains
simultaneously. Furthermore, by applying novel reconstruction methods 3D maps of
the grain boundaries can be generated. With the present 3DXRD microscope set-up at the European Synchrotron Radiation Facility, the spatial resolution is ~ 5 µm, while
grains of size 100 nm can be detected. 3DXRD microscopy enables, for the first time, dynamic studies of the individual grains and sub-grains within polycrystalline
materials. The methodology is reviewed with emphasis on recent advances in grain
mapping. Based on this a series of general 3DXRD approaches are identified for
studies of nucleation and growth phenomena such as recovery, recrystallisation and
grain growth in metals.
Abstract: A new technique for investigating 3D grain growth in polycrystalline materials using
white x-ray microdiffraction with micron point-to-point spatial resolution is presented. This technique utilizes focused polychromatic x-rays at the Advanced Photon Source, differential aperture depth-profiling, CCD measurements, and automated analysis of spatially-resolved Laue patterns to measure local lattice structure and orientation. 3D thermal grain growth studies of hotrolled aluminum have been initiated to demonstrate the capabilities of this method. Complete 3D grain orientation maps were obtained from a hot-rolled aluminum polycrystal. The sample was then annealed to induce grain growth, cooled to room temperature, and re-mapped to measure the thermal migration of all grain boundaries within the same volume region. Initial observations reveal significant grain growth above 360°C, involving movement of both low- and high-angle boundaries. Systematic measurements have been obtained of the as-rolled grain structure and of the microstructural evolution after annealing at successively higher temperatures. Small second-phase precipitates have been identified. Such measurements will provide the detailed 3D experimental
link needed for testing theories and computer models of 3D grain growth in bulk materials.
Abstract: The newly developed “sweeping detector” technique with high energy synchrotron radiation allows to measure textures and microstructures of materials with high location and orientation resolution. This method was applied to hot rolled aluminium manganese alloys and to rolled nickel samples in different recrystallization stages. The grain-resolved measurements show, impressively, many details of the recrystallization process which can otherwise not be seen. That can be the base for
comprehensive recrystallization theories.
Abstract: We present a novel electron detector and technique permitting orientation contrast images to be generated using back-scattered electron signals. The detector is a modification of the converter plate. It is unaffected by Infra-Red and light photons and invulnerable to the effects of heat. Consequently, the detector is removed as the temperature limiting factor in elevated temperature SEM grain observations. The detector has been successfully applied to an environmental SEM (ESEM) operating in high vacuum mode and has produced good quality video image sequences of hot metal specimens with frame rates between 1 per second and 1 per 30 seconds (largely material dependent). Temperatures attained were up to 850°C, limited by the capability of the hot stage. Although developed for the ESEM the technique is applicable to any SEM provided that adequate measures are taken to manage contamination and heat effects on other microscope components. We
have produced images and short, accelerated video sequences of recrystallisation and grain growth phenomena in steel, aluminium, copper and gold by the new technique. The technique has also successfully imaged phase transformations and high temperature behaviour of microelectronic materials.
Abstract: A method for in-situ studies of the dynamics of individual embedded subgrains during
recovery is introduced. The method is an extension of 3DXRD principles for studies of grain dynamics in connection with recrystallisation. It is limited to studies of foils with a sample thickness of 10-100 subgrains due to diffraction spot overlap. The volume evolution during recovery (annealing at 300°C for 181 minutes) of nine individual subgrains in a deformed sample (38% cold rolled Aluminium) is presented.
Abstract: This paper presents a method to estimate the stored energy during the tensile deformation of an aluminum multicrystal and polycrystal sheet sample. The method is based on thermo mechanical macroscopic fields analysis, like strains and temperature, obtained by a visible and an infrared cameras. Preliminary experimental results are presented. On an Al multicrystal sheet, heterogeneous thermo mechanical fields associated to the localized movement of dislocations at a
microscopic scale are presented. Furthermore, the energetic balance established during the tensile deformation of an Al polycristal show a decreasing ratio of stored energy on anelastic energy and a non constant fraction of total work converted into heat.
Abstract: Experiments in which the microstructural development can be observed at the same time as the crystallography is described fully opens up new, powerful ways to advance our understanding of microstructural processes such as grain growth, primary and secondary recrystallization and phase transformations. In addition, comparison of results of experiments in different materials can be used to develop general laws for the investigated processes. In this study, we briefly review and compare the results from various ongoing studies undertaken in a variety of
materials with emphasis on highlighting (a) the scientific potential of such experiments and (b)similarities and differences in their microstructural evolution. Materials studied include metals e.g. Ti, Ni, Al, Mg, Ti-SULC steel and geological materials such as rocksalt (NaCl), hematite and magnetite. Here, we present experimental results and their interpretation in terms of subgrain to grain-scale processes.