Cold deformation behavior and microstructure evolution of biomedical Cu-containing L605 alloy

The effect of copper (Cu) addition on the microstructure evolution and deformation mechanism of L605 (Co20Cr-15 W-10Ni) alloy during cold deformation was investigated by using transmission electron microscopy (TEM), X-Ray diffraction (XRD) and electron backscatter diffraction (EBSD) analysis. The results indicated that the addition of Cu slightly decreased the yield strength and ultimate tensile strength, while it significantly increased the elongation. EBSD results revealed that hexagonal close-packed (HCP) martensite was generated during cold deformation and increased with increasing cold deformation level. The deformation microstructure of both alloys at different cold deformation levels shows that the stacking faulting was the primary deformation mechanism at early stage of cold deformation, in contrast, dislocation planar-slip and face-centered cubic (FCC) to HCP martensitic transformation were prevailed at both medium and late cold deformation level. Cu addition significantly suppressed the dislocation and stacking fault multiplication at early deformation stage and delayed the martensitic transformation at medium and late deformation stage, which could be ascribed to the relatively high stacking faulting energy by Cu addition, resulting in the low strain hardening behavior in the entire deformation process. These cumulative results and analyses could provide a solid foundation for the further development of this novel type of biomedical Cu-containing cobalt-based alloy.