On the influence of repetitive corrugation and straightening on the microstructure and mechanical properties of AA 8090 Al-Li alloy

This paper reports on the improvements in the mechanical properties of AA8090 Al-Li alloy subjected to repetitive corrugation and straightening (RCS). AA 8090 Al-Li alloy sheets were processed using different corrugation profiles (semi-circular, flat-groove and V-groove) at 300 °C, with a pressing velocity of 2.5 mm/s. This study shows that a V-grooved die favors grain refinement, e.g. a reduction in the average grain size from 65 μm to 12 μm after eight passes is achieved. Grain size distribution and misorientation between grain boundaries were studied using EBSD and TEM. The microstructures also appear to have more high-angle grain boundaries in the case of the specimen processed using the V-grooved die. The tensile strength increases with the number of passes, but drops when surface cracks appear after the 16th pass for a semi-circular die, the 12th pass for a flat grooved die and the 10th pass for a V-grooved die. In contrast, the hardness continues to increase with increasing number of passes. Ultra-fine-/nano-grains were present after the eighth pass in a sheet that was processed using a V-grooved die.