Grain boundary formation stages in a deformed yellow gold single crystal studied by mechanical spectroscopy

A monocrystalline 18-carat yellow gold sample is deformed stepwise from 2% to 12% at room temperature. The mechanical loss spectrum is recorded and analysed. At low deformations the exponential high temperature background increases. At a critical deformation of 8% an intermediate temperature peak appears. Such peak typical of polycrystals is related to grain boundary sliding. The comparison of a polycrystal formed of low angle grain boundaries (LAGB) only, and samples deformed between 2% and 8% evidence the existence of an intermediate stage. The high temperature peak P3 characterizes the mobility of LAGB that is controlled by the movement of dislocations.