Microstructure and mechanical properties of Al clad Mg composite bars fabricated by continuous extrusion

Abstract

6063 Al alloy clad AZ31 Mg alloy composite materials were fabricated by continuous extrusion under different heating temperatures with various billet diameters. The composite bars with the size of ϕ5 mm were obtained. The microstructure and mechanical properties of the composite bars were analyzed by means of scanning electron microscope (SEM), optical microscope and tensile tests. The results show that grains in Mg core of the composite bars can be significantly refined by continuous extrusion. The average grain size of Mg core is 15.4 μm. The tensile strength of the composite material is 141.4 MPa and the elongation is 6.6% when the billets are extruded at room temperature. The average grain size of the Mg core increases with the heating temperature. In addition, the tensile strength of the composite material slightly decreases but the elongation is improved to 10% when the billets are extruded at the heating temperature of 450 ℃. Moreover, the microstructure shows more homogeneous and more refined grains by using a larger diameter of Mg core. The average grain size is refined to 12.8 μm. The results of SEM observation show that the interdiffusion occurs between Al and Mg during continuous extrusion. The largest thickness of the diffusion layer is 4.8 μm. The highest hardness is observed at the middle of the interface. At the same time, the material flow of Al-Mg during continuous extrusion is simulated by Deform finite element (FE) software. The temperature and strain distributions of Al and Mg are obtained by the FE simulation, which is helpful to understanding the microstructure evolution during continuous extrusion.

Keywords

• magnesium alloy
• aluminium alloy
• continuous extrusion
• composite material