Microstructural analysis of biomedical Co-Cr-Mo alloy subjected to high-pressure torsion processing

摘要

The effect of high-pressure torsion (HPT) processing on the microstructure and Vickers hardness of Co-Cr-Mo (CCM) alloys were investigated in this study. The microstructure of initial CCM alloy contains equiaxed grains with a grain diameter of approximately 50 urn and twins. The clear grain boundaries of equiaxed grains and twins disappear after HPT processing at a rotation number, N, of 10. The phase maps of initial CCM alloy and CCM alloy subjected to HPT processing at N= 5 measured by electron backscatter diffraction exhibit that the ratio of y phase decreases from 93.5% to 34.1% and the ratio of ￡ phase increases from 6.5% to 65.9% by applying HPT processing. These results indicate that the ￡ phase is formed by high-strain, which is induced by the HPT processing. The Vickers hardness values on the surfaces of the CCM alloys subjected to HPT processing at N = 1,5, and 10 increase with increasing the equivalent strain, εeq. These results suggest that an increase of Vickers hardness is correlated to an increase of the ratio of 8 phase and the dislocation density, and grain refinement, which are caused by the high-strain induced by HPT processing.