Age softening behavior of strip cast and direct chill cast Al-Mg alloys

The Aging Softening behavior of Al-Mg alloys was studied in 90% cold rolled Strip Cast (SC) AA5754 and AA5182 alloys. It was found that Al-Mg alloys show significant age softening after long time exposure at room temperature. In addition to age softening, the intensity of the Portevin-Le Chatelier (PLC) effect also increases with increasing aging time at room temperature. The tensile anisotropy decreases after long time room temperature aging. Crystallographic textures also reveal an aging effect when examined at room temperature for long times. The deformation texture components decrease in intensity while the recrystallization texture components increase in intensity with increasing time at room temperature aging. The intensity of the aging effect increases with increasing Mg content, increase in the degree of cold reduction, and increase in aging temperature. While no precipitation was observed in samples aged at room temperature for 1.5 years, precipitation was observed using both optical microscopy and TEM in samples aged at 204°C for 3 hours. These results support the hypothesis that the aging behavior results from the decomposition and precipitation of the Mg-rich clusters around dislocations.