Microstructural characterization of a cobalt-chromium-molybdenum alloy subjected to surface mechanical attrition treatment
Résumé
Surface Mechanical Attrition Treatment (SMAT) is a severe plastic deformation process that enhances the surface properties and the performances of a material by creating a nanostructured layer on the top surface of the material. SMAT has been shown to improve mechanical properties of materials such as hardness, strength, fatigue life and wear resistance. The process was applied to a CoCrMo alloy used in biomedical applications with the idea to improve its surface properties. The hardness of the material after SMAT was measured using nanoindentation and was shown to have almost triple in comparison with an untreated specimen. The changes in the microstructure due to SMAT were characterized using transmission electron microscopy, electron backscatter diffraction and transmission Kikuchi diffraction. It was observed that the formation of the nanostructured layer was driven by phase transformation; the alloy transforming from an fcc to an hcp phase under strain.