An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscat...An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscatter diffraction-scanning electron microscopy）, TEM （transmission electron in microscopy） and HREM （high- resolution electron microscopy）. The results reveal that the propagation of the shear band exhibits an asymmetrical behavior arising from inhomogenous distribution in plasticity in the bands because of different resistance to the collapse in different crystallographic directions; The γ-ε-α′phase transformations may take place inside and outside the bands, and these martensitic phases currently nucleate at intersections either between the twins and deformation bands or between the twins and ε-sheet. Investigation by EBSD shows that recrystallization can occur in the bands with a grain size of an average of 0.2μm in diameter. These nano-grains are proposed to attribute to the results of either dynamic or static recrystallization, which can be described by the rotational recrystallization mechanism. Calculation and analysis indicate that the strain rate inside the shear band can reach 2.50×10^6 s^-1, which is higher, by two or three orders of magnitude, than that exerted dynamically on the specimen tested.展开更多
A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate （β-TCP） was fabricated on pure magnesium via the chemical deposition in a simulated Hank’s solution. The method significantly accelerated t...A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate （β-TCP） was fabricated on pure magnesium via the chemical deposition in a simulated Hank’s solution. The method significantly accelerated the coating formation on magnesium. Moreover, the morphology, phase/chemical composition, the coating formation mechanism as well as degradation behavior in phosphate buffered saline （PBS） solution were in- vestigated. Scanning electron microscopy （SEM） images showed that the coating had three layers and X-ray diffraction （XRD） patterns showed that the coating mainly contained Ca3（PO4）2 and （Ca,Mg）3（PO4）2. Elec- trochemical test showed that the corrosion current density （Icorr） of the coated Mg was decreased by about one order of magnitude as compared to that of pure magnesium. The immersion test indicated that the coating could obviously reduce the degradation rate.展开更多
文摘An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscatter diffraction-scanning electron microscopy）, TEM （transmission electron in microscopy） and HREM （high- resolution electron microscopy）. The results reveal that the propagation of the shear band exhibits an asymmetrical behavior arising from inhomogenous distribution in plasticity in the bands because of different resistance to the collapse in different crystallographic directions; The γ-ε-α′phase transformations may take place inside and outside the bands, and these martensitic phases currently nucleate at intersections either between the twins and deformation bands or between the twins and ε-sheet. Investigation by EBSD shows that recrystallization can occur in the bands with a grain size of an average of 0.2μm in diameter. These nano-grains are proposed to attribute to the results of either dynamic or static recrystallization, which can be described by the rotational recrystallization mechanism. Calculation and analysis indicate that the strain rate inside the shear band can reach 2.50×10^6 s^-1, which is higher, by two or three orders of magnitude, than that exerted dynamically on the specimen tested.
基金supported by the National Natural Science Foundation of China (No. 30970715)the National Basic Research Program of China (973 Program,No. 2012CB619101)
文摘A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate （β-TCP） was fabricated on pure magnesium via the chemical deposition in a simulated Hank’s solution. The method significantly accelerated the coating formation on magnesium. Moreover, the morphology, phase/chemical composition, the coating formation mechanism as well as degradation behavior in phosphate buffered saline （PBS） solution were in- vestigated. Scanning electron microscopy （SEM） images showed that the coating had three layers and X-ray diffraction （XRD） patterns showed that the coating mainly contained Ca3（PO4）2 and （Ca,Mg）3（PO4）2. Elec- trochemical test showed that the corrosion current density （Icorr） of the coated Mg was decreased by about one order of magnitude as compared to that of pure magnesium. The immersion test indicated that the coating could obviously reduce the degradation rate.
