A study of serrated yielding, texture and formability of 5xxx series aluminum alloys

Serrated yielding, texture and formability were studied in 5xxx series Al-Mg alloys. Serrated yielding phenomenon occurred in all three alloys investigated when they were subjected to tensile tests. The underlying mechanism is widely accepted to be dynamic strain ageing, where mobile dislocations are repetitively locked and unlocked by solute atmospheres. Serrated yielding is characterized by the zigzag shape of the stress-strain curve. Among all three alloys, the intensity of serrated yielding increases with an increase in Mg concentration. By generating large grain-size microstructures through thermal-mechanical treatments, a decrease in serration intensity can be obtained.; Since Mg solute atoms are commonly believed to cause serrated yielding, a decrease in Mg concentration will lead to a decrease in serration intensity. In the same alloy (AA5182), this is achieved through a low temperature heat-treatment to precipitate Mg solute atoms. AA5182, with its highly super-saturated Mg concentration, displayed the most intense Mg2Al3 precipitation while there was no obvious Mg2Al3 precipitation in AA5052 due to its moderate Mg concentration. Studies also showed that Mn solute atoms caused a decrease in serration intensity. The decrease in Mn concentration therefore was found to lead to an increase in serration intensity. This is most significant in AA5182. Texture evolution during cold rolling was investigated in AA5182. It was found that the AA5182 alloy with Mg precipitation has different rotation rates of the texture components than the AA5182 alloy with Mn precipitation. The differences appear to be related to the different serration behaviors of the two materials.; Texture evolution during isothermal annealing of the 70% cold rolled AA5182 alloy with initial maximum and minimum serrations was investigated. It was found that the volume fractions of the texture components were different between the two materials. This difference is related to the particle structures of the two materials before isothermal annealing.; Formability tests were carried out on AA5182 alloy with the two initial conditions. The lower mechanical anisotropy of the Mg precipitation material is due to its more random texture. The material with Mn precipitation has better overall formability. This is related to its more uniform precipitation.