A thermodynamic description of the B-Co system: Modeling and experiment

The B-Co system is investigated via thermodynamic modeling and experiments. In the modeling section, all of the experimental phase diagram and thermodynamic data available from the literature were critically reviewed and assessed by using thermodynamic models for the Gibbs energies of individual phases. In the experimental section, 6 key alloys were prepared by arc melting Co slug and B pieces and annealing at 900 degreesC for 9 days. Water-quenched samples were analysed by using X-ray diffraction, optical microscopy, electron probe microanalysis and differential thermal analysis techniques. The measured invariant reaction temperatures are: 1136+/-2 degreesC for Liquid (L)<---->(alphaCO)+Co3B, 1157+/-2degreesC for L+Co2B<---->Co3B, 1263+/-2degreesC for L<---->Co2B+CoB, and 1358+/-2degreesC for L<---->CoB+B. A consistent thermodynamic data set for the B-Co system is finally obtained by considering the present experimental results and reliable literature data. Comparisons between the calculated and measured phase diagram and thermodynamic quantities show that all of the accurate experimental information is satisfactorily accounted for by the thermodynamic description.