Microstructure and thermal residual stress analysis of SiC fiber through Raman spectroscopy

SiC fiber-reinforced metal matrix composite is an interesting material for aerospace industry because of its excellent properties. However, these properties are greatly influenced by fiber microstructure and thermal residual stresses introduced by the preparation of the composites. Due to complicated preparation technology, microstructure and thermal stress along SiC fiber radius varies, which makes characterization difficult. Raman spectroscopy is a non-destructive technique which provides information, at micrometer scale, on the phase composition and the crystalline state (structure and texture) of materials. Line scanning was used to assess microstructure along SiC fiber radius embedded in Ti64. The SiC coating is subdivided into three concentric parts across the fiber diameter, according to the differences in intensity and width of SiC transverse optical phonon (TO) band. Part 2 is considered to be a buffer zone connecting Part 1 and Part 3 with different deposition conditions, respectively. Amorphous Si is detected throughout fiber radius, while crystalline Si is only detected in the outer part. Thermal residual stress along fiber radius in the composite was calculated by using SiC TO band shifts with a bare fiber as reference. A cylindrical model was also used to compare with the stress data obtained from Raman shift. Copyright (c) 2013 John Wiley & Sons, Ltd.