The process of TiB₂-Cu composite phase and structure formation during combustion synthesis

The reaction process of combustion synthesis for TiB₂-Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction (XRD) analysis, SEM analysis and differential thermal analysis (DTA). The XRD analysis results for the different parts of the quenched specimen show that TiCu_x inter-metallic phase firstly forms with the propagation of combustion wave, and then Ti_1.87B₅₀ and Ti₃B₄ metastable phases come forth due to the diffusion of B atoms and finally the stable TiB₂ phase forms because of the continuous diffusion of B atoms. The formation of TiB₂ phase is not completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages: melting of Cu and Ti, and the formation of Cu-Ti melt and few TiCu_x, TiB_x intermetallic phases; large numbers of TiCu_x intermetallic phases formation and some fine TiB₂ particles precipitation; and the TiB₂ particles coarsening and the stable TiB₂ and Cu two phases formation in the final product.