Effect of thermal treatment on mechanically milled cobalt powder

Stabilization of the metastable FCC phase has been achieved after 10 h milled Co powder sintering at 1400 °C. Phase identification of the Co powders was performed by the X-ray diffraction analysis, while the microstructural analyses were performed by scanning electron microscopy. Phase transformation on the metal was traced by the differential scanning calorimetry.

► Presence of ultrafine (amorphous-like) particles in the unmilled Co powder led to HCP/FCC cp-existence upon 1400C sintering.
► 10 h MM changed particle shape of Co powder from irregular-spherical to thin flakes.
► MM promotes thermal stabilization of metastable FCC Co due to produced thin flakes.
► Metastable RHL phase was detected on milled Co sintered at 1200 °C.
► High average hardness of 300 HV in sintered milled compacts was obtained compared to 50 HV of unmilled.