Microstructure and mechanical properties of 1060/7050 laminated composite produced via cross accumulative extrusion bonding and subsequent aging

Accumulative extrusion bonding (AEB), as a recently developed severe plastic deformation method, is a promising process for large-scale preparation of ultrafine-grained (UFG) materials. In this work, cross accumulative extrusion bonding (CAEB) was developed based on AEB to produce 1060/7050 laminated composite. TEM observation showed that the ED-elongated grain structures with the average grain width of 0.68 +/- 0.05 mu m and 1.80 +/- 0.2 mu m for 7050 and 1060 were formed, respectively. Tensile test demonstrated that the CAEB-processed laminated composite exhibited an outstanding combination of strength and ductility. And the CAEB-processed composite presented an extra strengthening that was higher than the predicted result by the rule-of-mixture. This extra strengthening mechanism is referred to as hetero-deformation induced (HDI) strengthening. Subsequent aging was applied to combine the CAEB process to further improve the mechanical properties of the CAEB-processed composite. After aging, the plate-like eta' phase and rod-like eta phase precipitates appeared in the 7050 layers. These nanoprecipitations play a significant role in precipitation strengthening. Further EBSD characterization revealed a bimodal grain-size distribution between the constituent layers. The 7050 layer with ultrafine grains provides the high strength, while the 1060 layer with coarse grains attains strain hardening. (C) 2020 Elsevier B.V. All rights reserved.