Dependence of microstructure evolution of novel CoreFlow™ aluminium alloy wire on wire diameter

The wire diameter Dr is one of the key parameters used to tailor the microstructure of alloy wires prepared using a novel room-temperature (RT), one-step CoreFlow™ process. However, the microstructural evolution of CoreFlowed wires at varying Dr remains unclear. The dependence of microstructure characteristics on the Dr should be considered in the future design of CoreFlowed wires. In this study, the microstructure evolution of CoreFlowed 6082 aluminium (Al) wires with four diameters (Dr = 1, 2, 3, and 4 mm) was systematically investigated. After the CoreFlow™, the average grain sizes of all CoreFlowed wires were less than 12 μm compared with the original Al sheet with a coarse grain of 2000 μm. As the Dr increases, the refinement degree of the grain decreases. Particularly, a gradient structure, characterised by grain size increasing from the edge to its centre along the radial diameter, is introduced into CoreFlowed wires. The difference in interaction between strain and heat during CoreFlow™ is responsible for the gradient in grain size. As the Dr increases, the grain size at the edge and its centre increases simultaneously, but the difference in average grain size between them decreases, which is related to the nonlinear change of heat and strain with the Dr. Moreover, the gradient distribution of grain size causes the gradient distribution of specific micro-texture components. The texture components in CoreFlowed wires show a great change with Dr, but their variations show a trend from recrystallization texture to deformation texture with an increase in Dr.