of commercial and high-purity non-heat-treatablealuminum alloys are investigated in this work. It is found that both magnesium and manganesei ns olid solution give an early linear concentration dependence of the strengtha tagiven strain for commercial alloys. This deviates from highpurity AlMg binary alloys, where aparabolic concentration dependence is found. Mn in solid solution is found to give ac onsiderably higher strengthening effect per atom than Mg, both in terms of yield stress and initial work hardening rate. This strengthening effect is stronger comparing commercial grades to high-purity alloys. This enhanced strengthening is believed to be as ynergy or clustering effect caused by interaction betweenMnatoms and trace elements, probably silicon, in solid solution.

The work-hardening behavior of arange of aluminum-magnesium alloys, from 0.5 to 4.55 wt pct Mg, is followed up to large strains using compressiontesting and cold rolling. At large strains, stage IV,an unexpectedly loww ork-hardening rate of high-Mg alloys is observed, and the work-hardening rate in stage IV is almost unaffected by the Mg content. Am odel for work hardeningi sa pplied and discussedi nr elation to the experimental observations. Based on microstructuralo bservations of the cold-rolled materials, the lowwork-hardening rateofhigh-Mg alloys is ascribedtoadifferent storage pattern of dislocations caused by an increased amount of shear bands and ahigher dislocation density inside subgrains.

Abstract. The strength and work hardening of age hardened AA6063 and AA6082 alloys have been investigated in terms of a detailed characterization of precipitate and dislocation structures obtained by TEM and SEM. Tensile and compression tests were performed at as quenched, peak aged and severely aged conditions. A strong work hardening in the as quenched condition was found, similar to AlMg alloys with twice as much alloying elements in solid solution. It was found that the initial work hardening rate and the critical failure strain are both smallest at the peak aged condition. During large deformations the needle-shaped precipitates are sheared uniformly by dislocations altering their <001> orientations, which indicates extensive cross slip. In the overaged condition the early initial work hardening is larger than at the peak aged condition, but followed by a weak linear work hardening, apparently directly entering stage IV at a low strain. Cracked, needle-shaped precipitates were seen at larger strains.

The work hardening of alloys hardened by precipitate heat treatments depends on the distribution of the precipitate sizes and the solute level left in the metal matrix. A mean field theory for precipitation is first applied for the ageing and subsequently it is coupled to a work hardening model to study the stress-strain responses of age hardened conditions of AA6xxx alloys. The predictions are compared to mechanical experiments and to TEM characterisations.

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