The role of alloying and the associated mutual interaction of solute atoms with dislocations on the stress and temperature dependences of the steady‐state creep rate is investigated for Al−2 wt% Mg. The high temperature steady state creep rate is measured for the annealed and pre‐coldworked alloy under stresses up to 17 kg mm−2. The stress sensitivity paremeter, m′, is calculated and amounted to about three for both cold‐worked and annealed samples. It is found, for temperatures less than 300 °C, that m′ is independent of the applied stress. The dependence of the apparent activation energy on stress shows that at relatively low stresses creep is controlled by selfdiffusion of Mg and at applied stresses higher than 15 kg mm2 most probably by cross slipping. Pre‐cold‐working the sample seemed to be ineffective on the mechanism controlling creep rate.

Work‐hardening tests are made on the precipitating binary alloy Al–2 wt% Mg. The yield and fracture stresses and the fracture strain are determined for test samples in the form of circular wires differently pre‐annealed at relatively high temperatures to produce different grain sizes. The precipitation of the β‐phase is fully effected by proper heat treatment at the start of the test. Controlled dissolution of the precipitate is then made in steps and the corresponding stress‐strain relations recorde dat constant strain rate. The yield stress, fracture stress, and fracture strain show a somewhat parallel behaviour indicating a peak value at a particular time of dissolution at each dissolution temperature. This peak is found to shift towards lower times of dissolution as the dissolution temperature increases. Taking the position of the peak as indicative to a certain degree of dissolution, the activation energy characterizing the process is found to be (1.22 ± 0.1) eV comparable with the diffusion energy of magnesium atoms in the aluminium matrix. The dislocation slip distance, as calculated from the parabolic work‐hardening coefficient, is found to be minimum near the forementioned peak conditions. Testing the present results with the Cottrell‐Petch relations indicates that the fracture mechanism is not located at the grain boundaries.

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