Atomic force microscopy of the intense slip localization causing fatigue crack initiation in polycrystalline brass

Abstract

For wavy slip materials like copper a recent nanotheory suggests that destabilization (splitting) of edge dipolar loops (EDLs) triggers formation of intense slip lines (ISLs), which nucleate persistent slip bands (PSBs) in a thermally activated process of cyclic saturation. The nanotheory also has implications for fatigue of planar slip materials like brass, which do not display saturation. Also has implications for polycrystalline brass (Cu–30% Zn) was cyclically strained at room temperature and constant plastic strain amplitude into the secondary hardening stage associated with nucleation of intense slip bands (ISBs). After unloading from compression and electropolishing to remove surface fatigue damage the specimen was loaded to its stress amplitude in tension. Slip lines formed during the tensile half-cycle were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and the observations were repeated after an additional compressive half-cycle.