The Mechanism of Void Growth and Factors Affecting the Onset of Intergranular Failure during Creep of a Mg–0·8% Al Alloy

Tensile tests on a Mg–0·8% Al alloy have been conducted at a strain rate of 10−2h−1 between 25 and 400° C with grain sizes ranging from 0·009 to 0·300 in. It is shown that the growth of voids occurs by a grain-boundary sliding mechanism and the variation of ductility in the intergranular-failure range is interpreted by means of this parameter. The factors that lead to the onset of intergranular failure are discussed in terms of the relative ease of nucleation and rate of growth of intragranuiar cracks and grain-boundary cavities.