Study of hot deformation of an Al-Cu-Mg alloy using processing maps and microstructural characterization

摘要

The forming behaviour of an Al-Cu-Mg alloy (Al 2024-T351) has been studied by processing maps and microstructural characterization. Torsion tests were conducted in the range 278-467 ℃, between 2.1 and 25.6 s~(-1). Stress-strain curves obtained from the experiment data were fitted using the Carofalo equation to obtain the constitutive parameters, obtaining a stress exponent of 6.1 and an activation energy of 180kJ/mol. Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure, before and after torsion testing, to evaluate the microstructural changes and instability phenomena. A peak ductility of the Al 2024 alloy was found at about 400 ℃ at all strain rates considered. According to the processing maps and microstructure observation, the optimum hot deformation condition for the Al 2024 alloy is in the range 360-410 ℃ and 2.1-4.5 s~(-1). Under these favourable conditions a uniform and fine grain size is obtained by extended dynamic recovery (DRV), which leads to the formation of subgrain boundaries that progressively transform at large strains into new high angle grain boundaries.