Effect of Zn, Mg, Cu, Zr on Microstructure and Properties of Laser Welding Aluminium Alloy

Abstract

A series of Al-6.3Zn-2.3Mg-2.3Cu-0.15Zr alloys with different reduce of Zn, Mg, Cu and Zr were prepared by ingot-metallurgy processing. The metallurgical structure and mechanical properties were investigated by optical microscope, scanning electron microscopy and other equipment. The results indicated that the ingot’s microstructures of the four alloys contain the phrases of η (MgZn2) and θ (Al2Cu), which mostly distribute at the grain boundaries in a shape of continuous network. After extrusion processing, the grain of laser welding aluminium alloy was elongated along the extrusion direction, therefore forming fibrous structures, and meanwhile the second phase particles with different degrees of fragmentation were arranged along the extrusion direction since the microstructure of extruded bars was inherited by the as-cast structure. Zr could significantly inhibit recrystallization of alloy; the recrystallization of the alloy with lower Zr was more obvious. As the content of Zr reduced, the tensile strength of alloy decreased, but the electrical conductivity and hardness increased. When the content of Cu was lower, the hardness were decreased.