Influence of cryorolling and post-heat treatment on microstructure, residual stress, and damping performance of AA2219 alloy

The current study investigates the effect of cryorolling and heat treatments on the microstructure, residual-stress profile, hardness distribution, and damping properties of AA2219 aluminum alloy. The material was subjected to cryorolling at −196 °C using liquid nitrogen. Afterward, various heat treatments, including low-temperature annealing (150–200 °C), intermediate annealing (250–300 °C), and conventional solution treatment followed by artificial aging (T6 state), were conducted. The cryorolling procedure resulted in significant plastic deformation, increasing dislocation density and subgrain formation. Grain refinement occurred mainly via a continuous recrystallization mechanism, in which dislocations gradually rearranged themselves, leading to low-angle boundaries turning into high-angle boundaries through subgrain rotation. Optical microscopic observations demonstrated a fine-grained structure (about 4.53 ± 0.90 μm) under the cryorolled condition. Additionally, grain growth occurred after the heat treatments. Using scanning electron microscopy in conjunction with energy-dispersive spectroscopy revealed precipitation of copper compounds (Guinier-Preston zones and metastable phases) during annealing and aging. Residual stresses appeared to be mostly compressive in the surface layers and tensile in the inner layers. The largest compressive stress was measured during intermediate annealing (∼−403 MPa). The highest hardness (∼110 HV) was achieved during low-temperature annealing, due to grain refinement and precipitation strengthening. Regarding damping properties, the most effective behavior was observed with intermediate annealing (∼0.063 at 30 Hz). It can be explained by increased dislocation mobility and precipitate interactions.