Overview No. 1: The nucleation of cavities by plastic deformation

Intergranular fracture at elevated temperature

The effect of interfaces on mechanical properties is considered. Elastic and plastic compatibilities at boundaries are treated. Specific influences at both low and high temperatures are discussed, with emphasis on dislocation mechanisms and the atomic scale structure of boundaries.

The influence of grain boundaries on mechanical properties

Creep cavitation in metals

The Nucleation of Cavities by Plastic Deformation

During the creep of magnesium, cavities form on some grain boundaries, limiting the ductility of the material and causing its density to decrease. It is shown that cavitation is eliminated if a hydrostatic pressure is superimposed which is equal to the creep stress. If the hydrostatic pressure is applied after cavities are already present in the material, continuing creep results in negligible density change and existing cavities do not continue to grow. When hydrostatic pressure is applied throughout the early stages of creep and is then removed, the subsequent cavitation develops at a rate which is unaffected by the prior deformation. The fractional change in density during creep is approximately proportional to the duration of creep to the power of 2·5 increasing to about 4 immediately prior to fracture. This rate of change of density is greater than can be accounted for by the growth of a constant number of cavities by vacancy condensation and suggests a progressive creation of nuclei. The nu...

G. W. Greenwood

Papers

The mechanism of cavitation in magnesium during creep