Densification mechanism, and microstructural evolution of W-Si-C composite consolidated via field assisted sintering

Abstract

Tungsten (W)-based composites with 1 wt% SiC were consolidated via field assisted sintering (FAST). FAST was conducted at temperatures ranging from 1000 °C to 1700 °C with holding times of 1–10 min under a pressure of 50 MPa. The densification and grain growth mechanisms were investigated using a creep deformation model and the grain growth power law. Various densification and grain growth mechanisms corresponded to different effective stress exponents (n) and grain growth exponents (p). n is the stress exponent associated with the densification mechanism, and p is the grain growth exponent related to the grain growth mechanism. The densification process mainly occurred at 1000 °C–1400 °C, whereas grain growth mainly occurred at 1500 °C–1700 °C. The W-Si-C composites were densified primarily through particle rearrangement (when n is ∼1), intergranular diffusion (when n is ∼2), and the dislocation-climb mechanism (when n is 3.62). The activation energies were estimated to be 153.80 and 541.17 kJ/mol at the effective stress exponents (n) of 1 and 2, respectively. Furthermore, intergranular diffusion is speculated to cause grain growth. The sintering temperature considerably affected the microstructure of W-Si-C composites. The silicide formed at sintering temperatures of <1100 °C was WSi2, and it transformed into W5Si3 with increasing sintering temperature.