Measurement of microscale residual stresses in multi-phase ceramic composites using Raman spectroscopy

Abstract

A methodology is described for characterizing the spatial distribution of thermal mismatch stresses at grain level in B 4 C-SiC-Si ceramic composites using Raman spectroscopy. Unlike traditional methods to detect residual stress (e.g., X-ray diffraction) which provide average values over the entire specimen surface, Raman peak-shift analysis provides residual stress distributions within the microstructure at high spatial resolution. While the classical formulation predicts uniform compressive stress within a Si-phase surrounded by the ceramic matrix, the Raman measurements revealed non-uniform residual stress distributions in Si when the particle size was larger than 5 microns. For large irregular shaped particles, the two methods coincide only along the interface between the particle and matrix, but vary drastically both in magnitude and nature in the interior of the particle where large tensile stresses have been measured. The average residual stress within the microstructure was found to correlate well with the volume fraction of the constituents and material properties. The presence of anomalous tensile stress in the interior of the minor Si-phase results in defect generation and structural disorder which has been confirmed by a subsequent TEM analysis.

Residual stress determination of silicon containing boron dopants in ceramic matrix composites

“…The wavenumbers are functions of the boron activation level, and thus the wavenumbers are lowered considerably as the activated boron increases near the center of the silicon vein. This phenomenon of decreased wavenumbers far from grain boundaries mimics the behavior of results from Jannotti et al; however, Jannotti did not take the half‐width or asymmetry of the reported Fano profiles into account, and reported large tensile stresses in these central areas that are likely to have been an erroneous interpretation of the data. Figure displays the half‐width of the Fano profiles per the investigated points of the area scan, which qualitatively illustrates the boron activation levels of the various points.…”

Residual thermal stress of SiC/Ti3SiC2/SiC joints calculation and relaxed by postannealing

“…Raman spectroscopy can be used to examine the microscopic nature of structural and/or morphological disorder, which is strongly correlated with the optical phonons in nanostructures . In the Raman spectra, the peak shifts relate to the residual stress, while the peak broadening and peak intensity decreasing reflect to structural disorder . The residual thermal stress can be determined by calculating the Raman sensitive peak shift.…”

“…The residual thermal stress can be determined by calculating the Raman sensitive peak shift. This has been employed to characterize the stress in B 4 C‐SiC‐Si composites and ZrB 2 ‐SiC composites . The Raman spectra of SiC near the interface (1‐2 μm away from the interface) were measured to investigate the residual stress near the interface.…”

“…32 In the Raman spectra, the peak shifts relate to the residual stress, while the peak broadening and peak intensity decreasing reflect to structural disorder. 33 The residual thermal stress can be determined by calculating the Raman sensitive peak shift. This has been employed to characterize the stress in B 4 C-SiC-Si composites and ZrB 2 -SiC composites.…”

“…This has been employed to characterize the stress in B 4 C-SiC-Si composites and ZrB 2 -SiC composites. 33,34 The Raman spectra of SiC near the interface (1-2 lm away from the interface) were measured to investigate the residual stress near the interface. Figure 3 shows Raman spectra of the as-obtained joining couples and after postannealed at 800°C, 900°C, and 1000°C, respectively.…”