Study of structural phase transformations in cobalt heat resistant alloys

Two Co–10 at % Al–5 at % Mo–2 at % Nb and Co–10 at % Al–7.5 at % Mo–3 at % Nb alloys of the Co-Al-Mo-Nb system were studied. Together with γ′→γ disordered transition, the formation of new intermetallic phase, which was suggested as Co2(Nb, Mo, Al)-type Laves phase, were found. This new phase decomposed at temperature range of 650–750°C. The precipitates of new phase were detected along the grain boundaries and inside the grains of the studied alloys.