The effect of erbium on the properties and microstructure of Al alloys

Mechanical properties, corrosion resistance, and microstructure of Al alloys with trace element erbium were studied. Systemic studies in the pure aluminum and 5xxx series Al alloys showed that the tensile strength was significantly improved by above 20% with little loss of elongation by Er alloying. The 5xxx series Al alloys with erbium also exhibited excellent corrosion resistance. Erbium improved the aging hardness response of 7xxx series Al alloys and the addition of 0.4%Er to Al-Zn-Mg alloys increases the hardness by 35MPa. In all experiment Al alloys, a small addition of 0.1wt% Er induced a quick increase of the tensile strength and the amount of 0.4%Er shows optimized balance of the strength and ductility. The Er addition improved the thermal stability, with increasing the starting Rex temperature about 50 degrees C in all investigated Al alloys. With regard to the microstructure mechanisms, in all experimental Al alloys Er addition has significantly refined the microstructure, which mainly attributed to presence the Al3Er particles. In the 7xxx series Al alloys, no observable PFZ after addition of 0.4% Er was found. The fatigue property, the fracture toughness and the thermal stability of microstructure and properties are on the way.