Microstructural characterization by electron backscatter diffraction of a hot worked Al-Cu-Mg alloy

Abstract

Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted in the range 278 to 467ºC, and at two strain rates, 2.1 and 4.5 s-1. Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure before and after testing. The microstructural evolution during torsion deformation at different temperatures and strain rate conditions determines the mechanical properties at room temperature of the Al 2024 alloy since grain refining, dynamic precipitation and precipitate coalescence occur along the torsion test. These mechanical properties were measured by Vickers microhardness tests. At 408ºC and 2.1s-1 the optimum combination of solid solution and incipient precipitation gives rise to maximum ductility and large fraction of fine and misoriented grains (fHAB=54%). In contrast, the increase in test temperature to 467ºC produces a sharp decrease in ductility, attributed to the presence of alloying elements in solid solution. Both the stress-strain flow curves obtained by torsion tests and the final microstructures are a consequence of recovery phenomena and the dynamic nature of the precipitation process taking place during deformation.