Effect of Mn‐Bearing Dispersoids on Tensile Properties and Recrystallization Resistance of Al‐3Mg‐0.8Mn Rolled Alloy

Herein, the precipitation behavior of Mn‐bearing dispersoids in Al‐3Mg‐0.8Mn (AA5454) alloy subjected to different heat treatments is investigated. The effects of Mn‐bearing dispersoids on the tensile properties and recrystallization resistance of the abovementioned alloy during hot/cold rolling and postrolling annealing are evaluated. The results show that a low‐temperature three‐step heat treatment (275 °C/12 h + 375 °C/48 h + 425 °C/12 h) generates a higher number density of Mn‐bearing dispersoids with finer sizes compared with the typical high‐temperature heat treatment (430 °C/2 h + 480 °C/2 h + 525 °C/2 h), thus resulting in significantly improved tensile strengths of hot/cold‐rolled sheets. After annealing at 300 °C, the yield strength (YS) of the alloy reached 196 MPa after hot rolling and 237 MPa after cold rolling, showing an improvement of 30%–32% over samples subjected to high‐temperature heat treatment. In addition, the low‐temperature heat treatment provides a higher recrystallization resistance after hot and cold rolling owing to the higher number density of Mn‐bearing dispersoids and the lower fraction of dispersoid‐free zones. The YS contributions of various strengthening components after hot and cold rolling are discussed based on constitutive models. The predicted yield strengths agree well with the experimental values.