Effects of Er on the microstructure and mechanical properties of an as-extruded Al-Mg alloy

The effects of rare-earth element Er on the microstructure and mechanical properties of an as-extruded Al-Mg alloy have been studied. It has been shown that without solution treatment after thermomechanical process, the addition of Er obviously decreases the yield strength, tensile strength and elongation of the as-extruded Al-Mg alloy. Microstructural analysis indicates that coarse constituents with Er and Mg have been formed in the alloys containing Er, and thus reduce the solubility of Mg in the matrix. The reducement of solubility of Mg decreases the interaction between Mg solute atoms and dislocations, and thus degrades the yield strength of the alloy. During deformation, the constituents with Er and Mg fracture first and act as the microcrack sources due to the stress concentration. The results indicate that solution treatment after thermomechanical process is a fundamental procedure to improve the mechanical properties of the Al-Mg alloys by the addition of Er element.