Microstructural characteristics and deformation behaviors of an Al–Mg–Si alloy with improved strength and conductivity processed by continuous casting and expansion extrusion

Abstract

The industrial applications of Al–Mg–Si alloys conductors still meet the big challenges of strength and conductivity trade-off. In the present work, a special continuous expansion extrusion forming (CEEF) with violent shearing deformation was performed on continuous cast 6101 Al alloy rods to process the sheets with improved mechanical and electrical properties by combining various artificial aging treatments. The results showed that refined dendrites with few intergranular phases and high supersaturation solid solubility could be obtained in the continuous casted rods with fast cooling rate. In the CEEF sheet, the gradient distribution of grain size from the core to the surface of the sheet was observed, where the grain size of processed sheet was refined remarkably by dynamic recovery (DRV) and dynamic recrystallization (DRX). When artificial aging was conducted on the as-extruded, solid-solution and pre-deformed alloy specimens respectively, different precipitation responses were found. The high-density dislocations in the pre-deformed alloy acted as pipes for rapid diffusion of solid solution atoms to accelerate their precipitation, reducing the matrix solid solution atom content and mitigating electron scattering phenomena. As a result, simultaneous improvements of strength and conductivity could be obtained by combining the above optimized strategies.