Study on microstructure and fracture characteristics of 5083 aluminum alloy thick plate

Abstract The microstructure and fracture characteristics of 105 mm thick 5083 aluminum alloy hot rolled plate are investigated by X-ray diffractometer, metallurgical microscope, scanning electron microscope, transmission electron microscope, energy dispersive spectrometer and tensile testing machine in this paper. The results show that the plate is mainly composed of α-Al, Al21(Fe, Mn)4Si, Al6(Fe, Mn) and Mg2Si. The second phase distribution is inhomogeneous along the thickness direction, resulting in an U shape change of elongation. The minimum elongation in Layer 5 is related to the dependence of Mg2Si on Fe-containing intermetallic compounds, state of dislocations and grooves. Al6(Fe, Mn) presents acicular in the surface layer and fragmented in the center, and its fracture mode can be used to roughly judge the stress. Under SEM, the common black phases in high Mg-containing aluminum alloys may be not Mg2Si, but holes formed by their shedding. Mg2Si tends to adhere to the surface of Fe-containing intermetallic compounds and it is more easily separated from Al matrix. This indicates that Mg2Si may be the source of stress concentration initially causing materials fracture. A comprehensive summary has been made to clarify the influence of structures on fracture characteristics of thick plate.