Abstract:
An Al-Zn-Mg-Mn-Zr alloy containing 0.26wt% Sc was melted, and then hot rolling, cold rolling, solid solution and aging heat treatment were carried out on the as-cast alloy in turn; Next, the alloy was welded by argon arc welding method using an welding wire with similar composition. The microstructure, tensile properties and hardness of welded joint were studied, and the existence form and acting mechanism of the trace amounts of Sc in the welded joint were discussed. The results show that weld zone contained typical as-cast dendrite microstructure. The heat affected zone was be divided into half fusion zone and softening zone. The half fusion zone was near weld zone and the zone contained a thin layer of equiaxed crystal microstructure; The softening zone was near the base metal and the zone was fiber microstructure and coarsening grains due to obvious recrystallization. The tensile strength, yield strength and elongation of the welded joint was about 481 MPa, 320 MPa, 9.97%, respectively, the welding coefficient of the weld joint achieved 0.826-8.28. Primary Al3(Sc,Zr) particles formed in the welded joint due to the trace amounts of Sc and Zr, the Al3(Sc, Zr) could act as the core of heterogeneous nucleation, consequently significantly refined as-cast grains in the molten pool. The variation tendency of hardness of the welded joint firstly increased, then decreased and then increased from the center of weld zone to base metal on both sides.