Phase diagram investigation and thermodynamic study of Os-B system

The constitution of the Os-B system was investigated in this work. The phase regions were determined by metallographic investigations. The existence of the following borides was confirmed: OsB_1.1 (hex.), Os₂B₃ (hex.) and OsB₂ (orthorh.), while the new high temperature Os₂B₃ compound with a not yet identified structure was observed. OsB_1.1 melts congruently at 1820±15°C and OsB₂ at 1870±15°C, while the solid solubility of B in Os was found to be less than 0.5 at%B. Considering thermodynamic study of this system, the activities and activity coefficients for osmium and boron were determined in temperature interval 3300-3500 K, based on the known liquidus and solidus lines from phase diagram, according to calculation procedure given by Rao and Belton. This revised version was published online in July 2006 with corrections to the Cover Date.