Long-term heat treatments on Ti6Al4V-SiCf composite. Part I - Microstructural characterization

The microstructure of Ti6Al4V-SiC(f) composite, in as-fabricated condition and after long-term heat treatments (up to 1,000 hours) in the temperature range 400 - 600 degrees C, has been investigated by means of high-temperature X-ray diffraction (HT-XRD), energy dispersion spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Particular attention was paid to the strains, arising during heating, and to the micro-chemical evolution of fibre-matrix interface. Micro-chemical examinations evidenced that a thin TiC layer has formed between the fibre carbon coating and the matrix during the fabrication process. TiC slows down further diffusion of carbon towards the matrix and guarantees the interface stability also for the most severe treatments examined here.