A direct extrusion-shear deformation composite process that significantly improved the metallurgical bonding and texture regulation grain refinement and mechanical properties of hot-extruded AZ31/AA6063 composite tubes

In this study, Mg/Al bimetallic composite tubes were prepared by direct extrusion-shear deformation (DESD) process. First, the influence of the shear deformation process on the bonding of Mg/Al composite tubes was determined. The results showed that compared with the direct extrusion process, the addition of shear deformation led to a bonding layer without cracks or defects. Second, the interfacial microstructure, texture evolution and mechanical properties of Mg/Al composite tubes subjected to different preheating temperatures were systematically studied. With increasing preheating temperature, the microstructure of the Mg layer showed uniform growth, while the microstructure of the Al layer grew which led to an increase in the basal texture intensity. The thickness of the intermetallic compounds (IMCs) increased as the preheating temperature was increased, while the bonding strength decreased. The decreased bonding strength was attributed to grain growth of the IMCs and hard-oriented grains near the Al side. In addition, the microstructure evolution of the Mg and Al layers in the DESD process was analysed. The results showed that shear deformation can effectively weaken the basal texture intensity of the Mg alloy and induce the transformation of the Al alloy texture from the deformation texture (Copper, Goss and S) to the recrystallization texture (Cube).