Development of a Co-20Cr alloy for potential biomedical applications

A Co-20 wt. Cr alloy was vacuum induction melted and cast into a wedge shaped copper mold. The resultant microstructures were investigated from sections obtained longitudinally and centrally in the plane normal to the diverging wedge faces. The aim of this work was to produce a microstructure free of interdendritic segregation with minimal or no intermetallic precipitates and suitable for biomedical implant applications. The as-cast microstructure consisted predominantly of columnar dendrites. In particular, the presence of athermal HCP e-martensite and the metastable FCC γ-Co phase were identified by X-ray diffraction means and scanning electron microscopy. It was found that the exhibited volume fraction of athermal e-martensite was over 90 wt. %. In addition, a heat treating below the γ/e transition temperature led to transformation of the athermal e-martensite into a stress-relieved isothermal one. In turn, the resultant tensile properties, ductility and fracture mode of the alloy