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Characterization of Co-Cr-Mo Alloys Used in HIP Implant Articulating Surfaces

Published online by Cambridge University Press:  10 February 2011

R. Varano
Affiliation:
Department of Metallurgical Engineering, McGill University, Montreal, QC H3A-2A7
J. D. Bobyn
Affiliation:
Jo Miller Orthopaedic Research Center, Montreal General Hospital, Montreal., QC H3G-IA4
S. Yue
Affiliation:
Department of Metallurgical Engineering, McGill University, Montreal, QC H3A-2A7
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Abstract

The microstructure, crystallography and mechanical properties of a wrought (ASTM F-1537) Co-Cr- Mo hip implant alloy were studied in this work. The effects of carbon content, heat treatment and room temperature compression on the above characteristics were also analyzed. Metallography of the asreceived material revealed the presence of ‘twins’ in a relatively fine microstructure with some randomly distributed grain boundary carbides. Heat treatment of the specimens produced a coarser microstructure, more uniformly distributed grain boundary carbides and annealing twins. Neutron diffraction of the specimens, which were deformed at room temperature, exhibited an increase in the volume fraction of the more stable Co-hexagonal closed-packed (HCP) crystal structure, due to a strain-induced transformation (SIT) from the metastable Co-face-centered cubic (FCC) crystal structure. It was also seen that the higher C specimens, as well as the heat treated specimens, possessed a lower volume fraction of the HCP phase. It was found, through shear punch testing, that the deformed specimens exhibited higher mechanical properties without any significant losses to the ductility of the material.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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References

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