Correlated transformation of the microrelief of the stressed surface of an amorphous alloy

Abstract

Samples of Fe70Cr15B15 and Fe77Ni1Si9B13 amorphous alloy foils are loaded at tensile stresses of 0.2–1.2 GPa under constant strain or constant stress conditions. The submicroscopic profiles of the surface are recorded on a scanning tunneling profilometer. The “instantaneous” or extended (in time) transformation of the surface relief is statistically described by calculating the autocorrelation functions of the change in the relief height along two-dimensional scanning paths parallel to the loading axis. The autocorrelation functions thus constructed allow one to estimate the correlation radii of the surface profile, i.e., typical scales of relief components (holes, protuberances, flat regions). The performed analysis has revealed a considerable spatial correlation (∼2 × 103 nm) between the relief components in both initial (unloaded) foils. The application of the tensile load leads to an immediate increase in the roughness of the relief and a sharp decrease in the correlation radius. Subsequently, the relief does not remain stable and changes as a result of competing processes, such as microcrack growth, leveling of bends, and nucleation of kink bands. The behavior of the autocorrelation functions adequately reflects the transformation of the surface profile.