The article analyzes the microstructure evolution of Co-Cr-Mo alloy during isothermal forging. The process of isothermal forging can be a technological solution to produce a semi-finished product for subsequent deformation processing and obtain a high-quality microstructure that excludes casting defects. Based on analysis of microstructure and phase composition and calculations, the required modes of ingot homogenization are determined. Finite element method simulation of the forging has shown that temperature and deformation conditions make deformation in the single-phase γ-region possible. However, at lower temperatures, σ-phase particles may precipitate at the last steps of deformation. After isothermal forging and water quenching, a mixture of recrystallized and polygonized structures with an average grain size of 5–10 μm and precipitation of ultra-fine dispersed particles of σ-phase (~0.13 μm) at grain boundaries are formed. Isothermal forging in the temperature range of 1100–1200 °C and at low strain rates of up to 1 s⁻¹ allows obtaining a microstructure without pores, cracks, and large inclusions. Thus, it makes it possible to use the forging billet for further deformation by different metal forming methods.

Co-Cr-Mo alloys are in high demand as materials for medical implants. However, hot processing of these alloys is quite difficult due to the need to maintain narrow temperature range of deformation to achieve the required mechanical properties and structure of the products. The features of formation of structure, phase composition and mechanical properties of Co-Cr-Mo alloy at the main stages of thermomechanical treatment were considered in this study. The results demonstrated a significant enhancement in the strength characteristics of the alloy during processing in both forging and radial shear rolling (RSR). At the same time, radial shear rolling processing simultaneously increased the strength and ductility of the alloy. According to the XRD analysis data, the phase composition changes from single-phase structure (FCC-phase) after forging to a mixture of FCC-phase and HCP-phase after RSR during processing. The structure gradient characteristic of RSR decreased as the total elongation ratio increased, maintaining a tendency towards a finer-grained structure near the surface of the bars and a coarser one in the center. This tendency was reflected in the average grain size and the level of mechanical properties. Combined thermomechanical treatment, including the RSR process, made it possible to achieve a unique formation of microstructure and phase composition in the Co-Cr-Mo alloy, ensuring high strength while maintaining ductility.