Submicron-scale depth profiling of residual stress in amorphous materials by incremental focused ion beam slotting

This paper reports a new technique, namely the incremental micro-slotting cutting method, for the investigation of residual stress profiles as a function of depth on a micron scale. The residual-stresses in a peened bulk-metallic glass (BMG) (Zr ₅₀Cu ₄₀Al ₁₀, in atomic per cent) are estimated using finite-element analysis of the surface relaxations, as measured by digital image correlation analysis from field-emission gun scanning electron microscopy images, which occur when a micro-slot is stepwise micro-machined by focused ion beam. The calculation algorithm, which solves this inverse problem of residual-stress estimation, is based on the unit pulses method and is stabilized by a Tikhonov regularization scheme. It is demonstrated on a peened BMG that the new technique allows residual-stress profiles in amorphous materials to be inferred with high spatial definition (∼400 nm). Observations point to the scalability of this method to study residual-stress profiles in volumes as small as 1 × 1 × 0.2 μm ³ or less, and is particularly well suited to glasses, but can also be applied to crystalline materials.