1Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Av. Universidad 3000, Circuito Exterior S/N, Cd. Universitaria, 04510, Mexico, D. F., Mexico
2Materials Science and Engineering Department, CEAS, University of Wisconsin-Milwaukee 3200 N. Cramer Street, Milwaukee WI 53211, USA
Adv. Mater. Lett., 2018, 9 (4), pp 291-295
Publication Date (Web): May 17, 2018
Copyright © IAAM-VBRI Press
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 after the heat treatment exhibited significant changes. Finally, preliminary tests in artificial saliva indicated that the heat-treated alloy possesses appreciable corrosion resistance when compared with other Co-alloys, making it an ideal candidate for dental implants.
Cobalt alloys, rapid solidification, athermal martensite, biomedical alloys.