Interaction of Molybdenum with Copper–Silicon Melts

Abstract

The solubility of molybdenum in copper–silicon melts and the kinetics of growth of Mo₅Si₃ and MoSi₂ layers on the molybdenum–melt interface at 1200 ⁰C are studied. An expression for description of molybdenum solubility in the melts at 0.20–0.36 at. parts Si is derived: lgX_Mo = –2,587 + (3,282)X_Si. The dependence of the growth rate constant of the Mo₅Si₃ phase layer on the activity of silicon in the 9–15 wt.% Si melt is established: k_Mo-Si = –0,3806 + 65,191)а_Si. It is shown that two phases form at 20 wt.% Si: Mo₅Si₃ and MoSi₂. Their thicknesses are 29.8 ± 2.9 µm and 25.7 ± 2.8 µm, respectively. The time dependence of the Mo₅Si₃ layer growth rate in Cu–Si melts is established to obey a parabolic law. The melt composition at the three-phase equilibrium Mo–Mo₅Si –melt is found as follows (at. parts): X_Si = 0,147; X_Mo = 7,86 · 10^–3; the rest is copper. At 35 wt.% Si, only the MoSi₂ phase is formed at the interface.