Hot compression deformation characteristics and microstructural evolution of a Co-Cr-Mo-C alloy: Effect of precipitate and martensitic transformation

The hot compression behavior of a Co-Cr-Mo-C alloy was studied in the temperature range of 1100-1200 °C and the strain rate of 0.001-1 s−1. The influence of processing parameters including temperature and strain rate on the microstructure of the alloy was investigated. The flow curves of the hot compressed samples at the investigated deformation temperatures and strain rates exhibited single peak stress. The effect of the strain rate and temperature of deformation on the flow stress was studied using a hyperbolic sine-type equation. The calculated activation energy was about 744.5984 kJ/mol. The evidenced microstructural characteristics combined with the shape of the flow curves indicate that there is a competition between dynamic recrystallization (DRX) and precipitation phenomena, especially at low strain rates, i.e. 0.001 s−1. The formation of precipitates at the grain boundaries prevent the mobility of boundaries and also cause the partial inhibition of the dynamic recrystallization. Whereas, long time for the precipitates coarsening causes the predomination of dynamic recrystallization. Thus, the serrated boundaries in microstructure along with oscillation in the flow curves take place due to this competition.