Dislocation Climb and Determination of Stacking-Fault Energies in Al and Al-1% Mg

Abstract

Quenching and annealing experiments on bulk specimens and hot‐stage investigations of climb of loops in thin foils have been made on Al‐1% Mg, and the results compared to those for pure aluminum. One percent Mg in solid solution has no effect on the type of loop produced after quenching nor on the precipitation of vacancies after subsequent aging. As in pure aluminum, quenching stresses determine whether Frank or perfect loops are formed in the alloy. Magnesium has little effect on the climb rate of loops, the activation energy being in the range 1.2–1.28 eV, which is similar to the values obtained by identical experiments on pure aluminum. It is concluded that the vacancy‐magnesium‐atom binding energy is extremely small. The stacking‐fault energies were estimated by comparing the rates of climb of large Frank and perfect loops in the same area of the foil so as to minimize the errors that arise if only the climb of Frank loops is measured. The stacking‐fault energies were determined to be 190±10 erg/cm² for Al‐1% Mg and 210±10 erg/cm² for pure Al.