Influence of microstructural modifications induced by ultrasonic impact treatment on hardening and corrosion behavior of wrought Co-Cr-Mo biomedical alloy.

摘要: In this work, biomedical Co-28Cr-6Mo alloy is subjected to ultrasonic impact treatment (UIT). XRD, TEM and SAED analyses show that the plastic deformation induced by UIT process results in a complex microstructural formation surface layer of alloy. The peculiar feature observed structure Lomer-Cottrell locks originated simultaneous sliding Shockley partial dislocations intersecting planes. At beginning (till strain extent e ≈ 0.2), dislocation pile-ups are gathered front stimulating great number chaotic stacking faults (SFs) packets (incompletely transformed martensite), which predominant with regard occurrence e-martensite micro-twins. incompletely martensite hinders shear translation through twin boundaries suppresses grain subdivision at used. On-going 0.4 leads further modification microstructure micron-scale γ-grains, consists numerous locks, subtraction SFs, intersected nano-twins fine lathes average size approx. 50-100 nm. structural features (at 0.4) allow adequately explaining noticeable increase microhardness without any cracks/cleavages layer. Enhanced corrosion resistance alloy, manifests itself less negative potential lower passivity currents potentiodynamic curve, promoted oxide films following features: CSL type γ/e interfacial boundaries, uniformly distributed carbides, high fraction grains oriented close packed (111)γ (0002)e planes parallel UIT-processed specimen.