The preparation of ZK61/7075 laminated composite by introducing pure Cu transition layer: Effect of extrusion temperature on microstructure and mechanical properties

This study successfully prepared 7075/ZK61 laminates containing pure Cu transition layers using extrusion technology, overcoming the non-formability issue of direct 7075/ZK61 stacked extrusion. The influence of extrusion temperature on the microstructure and mechanical properties of laminates was systematically studied. The results indicated that the extrusion temperature had no significant effect on the grain size of 7075, which was mainly composed of deformed grains. Simultaneously, many precipitates were formed in the matrix, and their quantity increased with rising extrusion temperature. In contrast, the ZK61 layer displayed recrystallized grains whose size increased with extrusion temperature. Furthermore, the angle between the grain c-axis of the ZK61 and the extrusion direction increased with rising extrusion temperature, while dislocation density in both layers decreased. Mechanical results showed that the strength of laminates increased with rising extrusion temperature. Specifically, at an extrusion temperature of 450 °C, the laminate exhibited the highest yield strength (YS) of 203 MPa and ultimate tensile strength (UTS) of 378 MPa. However, the ductility of the laminate was inversely proportional to the extrusion temperature, with the maximum elongation (EL) of 19.3 % at 330 °C. The enhanced of YS was attributed to a lower Schmid factor for basal slip in the ZK61 and an increased number of precipitates in the 7075. The decrease in plasticity was related to the grain coarsening in the ZK61 layer, the reduced SF and geometric compatibility factor for basal slip due to texture, and the increased quantity of precipitate phases in the 7075 layer.