Raman Investigation of Interfacial Reaction Product of SiC_f/Ti43Al9V Composite

Abstract

Interficial reaction products of 800°C heat‐treated SiCf/Ti43Al9V are studied. EDS mapping indicates two layers existence in the interface with different element enrichment. Raman line scanning along interface also shows two layers with TiCx next to SiC fiber and Ti2AlC next to matrix. Excess carbon throughout the interface and accumulation in TiCx layer is confirmed by Raman. FWHH of both D and G peaks indicate carbon in Ti2AlC layer is more disordered than that in TiCx layer. According to G peak and I(D)/I(G), carbon in interface can be assigned to disordered carbon with perfect graphene units size (La) stays around 0.7–0.9 nm. Raman peaks of Ti2AlC vary with same trend throughout Ti2AlC layer is detected, and Raman spectra of Ti2AlC near TiCx layer is different from that near TiAl matrix, which results from residual stress and TiC intergrowth with Ti2AlC due to lack of Al.

Temperature-dependent evolution of interfacial zones in SiCf/C/Ti17 composites

“…In the initial stage of HIP, the amorphous C layer and the ne-grained I RL were considered as the reaction fronts triggered by the interdiffusion between C and Ti, in which diffusion entry into turbostratic C of trace metal atoms induced its amorphization, on the other hand, diffusion towards the Ti17 matrix of large amount of C atoms provided sufficient reaction atoms and high nucleation rate, evidenced by the observed nano-composited structure of nc-TiC phase embedded into an amorphous C matrix, promoting the formation of ne-grained I RL. 14,22 The initial stage of HIP has been described as reaction-controlled process, 23,24 during which nanocrystalline nc-boundaries provided short-circuit paths to the diffusion of amorphous C. 25 During the process of C atoms passing through I RL, obvious grain growth of Ti matrix took place at zones nearby I RL simultaneously, thereby forming near-stoichiometric II RL through further reaction, which was responsible for the abrupt increment in grain size to $200 nm in II RL. This new production of compacted TiC II RL could be regarded as a diffusion barrier layer, 26 and the further interfacial reaction would be determined by diffusion-controlled process, during which the interfacial reaction rate was governed by the diffusivity of C through the formed TiC II RL, 24 since the diffusivity of C in TiC is several orders larger than Ti.…”