Effect of inter-annealing between two stages of extrusion on the microstructure and mechanical property for spray deposited Al–Cu–Li alloy 2195

Abstract

The spray deposited alloys need to be first extruded to reduce porosity, and then the extrusion is conducted again for final profile forming. It is required to carry out an inter-annealing between the two stages of extrusion. In this study, billets after the first extrusion were annealed with different parameters, and the effect of annealing process on the microstructure was investigated. Then the annealed billets were extruded again to obtain the extruded plates. The role of inter-annealing processes on the properties of extruded plates was investigated through microstructure characterization and mechanical properties testing. The results show that the inter-annealing processes increase the width of extrusion fibers and lead to static recrystallization in the extruded billets. The //ED texture in extruded billets increases obviously after the inter-annealing due to the static recrystallization. The solubility of the secondary particles can be increased with the inter-annealing temperature and holding time, which thus enhances the effect of solution strengthening. The billets annealed with higher temperature and longer time exhibit stronger deformation resistance owing to the high solution strengthening effect. After the second extrusion, the texture of //ED is introduced into the extruded plates, which causes apparent anisotropy of mechanical properties. The plates extruded by the billets with different inter-annealing parameters have similar microstructures, which thus results in similar mechanical properties. However, after solution and aging treatments, the extruded plate with inter-annealing at high temperature for a long time shows significant performance degradation, which results from the severe grains coarsening. Keywords: Extrusion, Inter-annealing, Al–Li alloy, Spray deposit forming, Microstructure, Mechanical properties