The influence of microstructure on the work hardening behavior of pure aluminum was studied by means of tensile tests at 77K on samples that had been treated to introduce or eliminate subgrains. A recrystallized or well-annealed microstructure, free of subgrains, develops well-defined dislocation cells when deformed, and has a work hardening rate that decreases rapidly with increasing stress. In contrast, when the test sample is recovered, subgrains form which hinder the formation of dislocation cells. As an apparent consequence, a high rate of work hardening is retained at high stress, which leads to an improved combination of strength and elongation.
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