Abstract:

An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate (≈104 s-1) deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM (electron backscat-ter 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 asymmet-rical behavior arising from inhomogenous distribution in plasticity in the bands because of different resistanceto 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 0.2 μm 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 2.50×106 s-1, which is higher, by two or three orders of magnitude, than that exerted dynamically on the specimen tested.

Key words: High-strain rate deformation, Adiabatic shear band, Electron backscatter...