Improving the elevated-temperature mechanical properties of AA3004 hot-rolled sheets by microalloying with Mo and optimizing the process route

The present work investigated the influence of Mo addition and thermomechanical process routes on microstructural evolution and elevated-temperature mechanical properties of Al–Mn–Mg 3004 alloys. Various combinations of heat treatment and hot rolling were applied to fabricate hot-rolled sheets. The results revealed that microalloying with Mo and two-step heat treatment increased the number density and volume fraction of dispersoids and decreased the volume fractions of dispersoid-free zones. The different processing routes had important impacts on microstructural evolution. The alloys processed with heat treatment followed by hot rolling had finer and better distributions of dispersoids than those subjected to hot rolling prior to heat treatment. The former resulted in higher tensile strengths at room and elevated temperatures. Among all conditions, the Mo-containing alloy subjected to two-step heat treatment followed by hot rolling exhibited the highest elevated-temperature properties and reached a yield strength of 93 MPa at 300 °C. Both the base and Mo-containing alloys subjected to two-step heat treatment followed by hot rolling showed excellent thermal stabilities up to 350 °C and almost no significant change in yield strengths after thermal exposure at 300–350 °C for 100 h.