Fatigue testing of single crystalline Si was performed in a temperature and strain rate domain where lattice friction was effective: 1073–1173K and 3 x 10−4/s. Tension–compression loading was applied to samples oriented for single slip, under plastic strain amplitude control. For plastic strain amplitudes ranging from 6 x 10−4 to 10−2, cyclic stress–strain curves exhibited 2 different stages of hardening and passed through a maximum before saturation was reached. Contrary to what was observed in face-centered cubic metals, the maximum and saturation stresses decreased when the strain amplitude per cycle was increased. Surface observations suggested that strain localization took place near to the maximum cyclic stress and beyond. Transmission electron microscopic observations revealed several kinds of typical dislocation arrangement, which were rather different to those observed in Cu. Before the maximum stress, thick rectilinear walls made up of edge dislocation dipoles were the main feature. When observed perpendicularly, those walls formed more or less corrugated arrangements. After the maximum stress was reached, the plastic strain seemed to concentrate into much thinner walls while, in inactive areas, the dislocation structure annealed; converting the dipolar walls into rows of prismatic loops. Active areas were much broader than the persistent slip bands, with the well-known ladder structure, that were observed in Cu.

Cyclic Deformation of Silicon Single Crystals - Mechanical Behaviour and Dislocation Arrangements. M.Legros, A.Jacques, A.George: Materials Science and Engineering A, 2004, 387-389, 495-500