Grain Boundary Precipitation and Fracture Behavior of Al–Cu–Li Alloys

Abstract

Several microstructural factors have been proposed to explain the intergranular fracture exhibited by Al alloys, including grain boundary precipitates (GBPs) and precipitate free zones (PFZs), Li segregation at grain boundaries, and planar slip producing high stress concentration at grain boundaries. We present here the nature of grain boundary precipitate and the interfacial characteristics of precipitate matrix interface of Al–3Cu–2Li and Al-8090 alloys using transmission electron microscopy (TEM) and the density functional theory (DFT) calculations. The fracture surfaces for both alloys are intergranular in nature. We show that the grain boundary microstructural feature, particularly the grain boundary precipitate matrix interface, is mostly responsible for dictating the fracture behavior.