13 research outputs found
Influence of Y2O3 nanoparticles on the twinning of single crystalline magnesium
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X-Ray Microdiffraction Characterization of Deformation Heterogeneities in BCC Crystals
The deformation behavior of BCC metals is being investigated by x-ray microdiffraction measurements (mu XRD) for the purpose of characterizing the dislocation structure that results from uniaxial compression experiments. The high brilliance synchrotron source at the Advanced Light Source (Lawrence Berkeley National Lab) and the micron resolution of the focusing optics allow for the mapping of Laue diffraction patterns across a sample. These measurements are then analyzed in order to map the distribution of residual stresses in the crystal. An important findingis the observation of Laue spot "streaking," which indicates localized rotations in the lattice.These may represent an accumulation of same-sign dislocations. Theoretical modeling of the diffraction response for various slip systems is presented, and compared to experimental data. Preliminary results include orientation maps from a highly strained Ta bicrystal and a less highly strained Mo single crystal. The orientation maps of the bicrystal indicate a cell-like structure of dense dislocation walls. This deformation structure is consistent with previous OIM studies of the same crystal. The results suggest that mu XRD may be a particularly useful tool for microscale studies of deformation patterns in a multi-scale investigation of the mechanisms of deformation that ranges from macroscopic deformation tests to high resolution TEM studies of dislocation structures
Investigation of microstructure and mechanical properties of Fe-V dissimilar welds
This paper presents a systematic investigation of solidification and phase formation, microstructures, and mechanical behavior of Fe-V weld metals. It is found that V weld metal is dominated by Fe25V solid solution (hardness ~ 6.1 GPa) with V-rich precipitates formed along the grain boundaries. The observed intergranular cracking is attributed to the phase separation of (αFe, V) solid solution into V-rich (V) and V-poor (Fe25V) regions at low temperature. The overall mechanical properties could be improved by using Cu20V composite filler, due to the formation of stable Fe10V and Cu solid solution phases