Interface reaction in the B4C/(Cu–Si) system Original Research Article

The instability of boron carbide in contact with liquid copper triggers the interaction between B4C and the melt. In a silicon-free melt, this interaction leads to the dissolution of boron in the liquid Cu with a concomitant release of free carbon. The compositions of the substrate and of the melt are adjusted according to the equilibrium requirements in the three-phase (B4C–graphite–liquid solution saturated with carbon) system. In the course of the interaction between boron carbide and the Cu–Si melt containing less than 13 at.%Si, no silicon carbide is formed and the liquid does not wet the substrate. For a silicon content higher than 13 at.%, the presence of graphite particle agglomerates within a crater, which is formed as a result of the initial decomposition of boron carbide, offers appropriate sites for the nucleation and subsequent growth of SiC particles. The interaction between the Si-containing melt and the B4C substrate leads to an enrichment of the melt with boron released from the substrate. In the vicinity of the triple line, the composition of the near-surface substrate layer is shifted to higher boron content and the conditions for wetting the substrate are met.