Characteristics of grain boundary migration and sliding during fatigue of high purity lead

Samples of high purity Pb were tested under conditions of low cycle reverse bending fatigue at a high homologous temperature. Inspection showed that the grain boundaries migrate in a regular and cyclic manner and, under conditions of constant frequency and strain amplitude, the average amounts of migration, m̄, and sliding, v̄, both increase with the number of loading cycles, N. If N is maintained constant, the values of m̄ and v̄ increase with increasing strain amplitude. Grain boundary cracking was observed after testing through 25 cycles at the higher strain amplitudes. These results confirm that the formation of intercrystalline cracks and cavities occurs more easily in cyclic loading than under conditions of uniaxial tension.