Microstructures and mechanical properties of spray deposited 2195 Al-Cu-Li alloy through thermo-mechanical processing

Abstract

A large-scale billet of 2195 Al-Cu-Li alloy was prepared by spray deposition technology. The hot extrusion, solution treatment, pre-stretching, and aging treatment were performed on the deposited billet. It was found that the yield strength, ultimate tensile strength and elongation of the T83-treated alloy reach 600 MPa, 632 MPa and 10%, respectively. The microstructures of the deposited alloy in the thermo-mechanical processing were studied by optical microscopy, scanning electron microscopy and transmission electron microscopy. The mechanical properties were examined by tensile test. It was found that the spray deposited alloy presents a microstructure with fine equiaxed grains and low segregation degree. After hot extrusion, a typical fibrous structure with incomplete recrystallization is formed. After solution and aging treatments, lots of T1 and δ′ phases precipitate in the matrix, leading to significant increase of the tensile strength. Pre-stretch prior to aging treatment produces a fine homogeneous distribution of the T1 plates throughout the matrix, which lead to an excellent tensile performance. The ductility of aged alloys is affected by the microstructure of grain boundary. Narrow precipitate free zone and dispersed grain boundary precipitates with small size are beneficial to improvement of alloy's ductility.