FORMATION AND ANNEALING BEHAVIOUR OF MULTI-FAULTED LOOPS IN AN ALUMINIUM-MAGNESIUM ALLOY

The electron microscope examination of quenched aluminium containing 0.65 wt.% of magnesium has revealed the presence of double-faulted, multi-component double-faulted and triple-faulted dislocation loops. The annealing rate of the double-faulted loops has been investigated as a function of temperature and the extrinsic stacking fault energy determined to be 157 ergs/cm2 or 1.4 times greater than the intrinsic fault energy. The stability of the inner fault has been studied in annealing experiments on the multi-component double loops and the results confirm previous assumptions that the second fault is nucleated on the next-nearest (111) plane above or below the primary stacking fault. The annealing kinetics of triple-faulted loops are in excellent agreement with those expected from a structure based on the condensation of three layers of vacancies on neighbouring planes. A new defect consisting of an annulus of stacking fault is concluded to have been formed during quenching from a triple loop in which the region of extrinsic fault has been erased by growth of the inner perfect loop. © 1969.