Microstructures and properties of 6063 aluminium alloy as-cast modified by rare earth element Er

The 6063 aluminium alloys with different Er content were prepared after composition design.The microstructure and properties of Er-Al alloy as-cast were investigated by an optical microscope,SEM,EDS,XRD and Vickers hardness tester.The effect mechanism of Er was theoretically analyzed.Results show that when Er content reaches 0.4%,the grain refining effect is best and the hardness increment is the most;when Er content over 0.4%,the grain refining effect is weaken and the hardness decrease gradually.In the course of solidification,most Er is segregated at grain boundaries,and forms coarse intermetallics Al3Er which lead to strengthening grain boundaries and inhibiting grain growth.A little portion Er and Al form into secondary intermetallics which dispersedly distribute in the substrate and strengthen the substrate.This dispersed phase works as nucleating agents and refines grains.