Localized vs homogeneous deformation in Fe82B15Si3 amorphous alloy

Abstract

Amorphous alloys are known to deform plastically either by a localized shear mode or in a homogeneous manner. Conditions that favor homogeneous deformation in an amorphous alloy consisting of 82Fe, 15B and 3Si in at. pct have been established by a free-bend test over a range of temperatures. These results are in turn related to the stress-strain rate-temperature relationship obtained by a load relaxation testing method. The intense, localized shear deformation is shown to occur at relatively high strain rate and low temperature regions where the rate sensitivity of flow stress,m, is small. With increasingm, plastic flow tends to take place homogeneously provided that the mode of deformation remains stable. The strain rate sensitivity of flow stress increases with decreasing strain rate and increasing temperature; the computed diffuse shear transformation zone also changes in the same manner. However, the general trend changes above the glass transition temperature, i.e., the diffuse shear transformation zone decreases and the flow strength increases with increasing temperature.