Effects of Sc on laser hot-wire welding performance of 7075 aluminum alloy

Abstract

In order to clarify the effects of Sc modification on laser hot-wire welding performance of 7075 high strength aluminum alloys, the changing rules of weld formation, microstructure, element loss, mechanical performances and pores of weld joints were investigated during laser fusion welding, laser hot-wire welding and Sc-modified laser hot-wire welding. Comparing with laser fusion welding, the filler wire in laser hot-wire welding brought welding material and hot wire energy, resulting in better weld formation and sufficient fused weld joint. In laser hot-wire welding, tensile strength and elongation of weld joint were enhanced, element loss of weld joint was dramatically reduced and weld pore was reduced slightly. However, grains in fusion zone were relatively coarse, which caused lower microhardness in laser hot-wire welding. In Sc modified laser hot-wire welding, Sc modification led to smooth and continuous weld joint. During solidification of weld joints, Sc could combine with base metal to form Sc-containing alloy phase, which could lead to the formation of refined and equiaxed grains, thereby enhancing the yield strength of microstructure and increasing the microhardness, tensile strength and elongation of weld joint. In addition, Sc modification could increase the fluidity of molten pool, which thus promoted the escape of bubbles from the molten pool and hindered the formation of weld pores.

Research Progress of Aluminum Alloy Welding/Plastic Deformation Composite Forming Technology in Achieving High-Strength Joints

“…For example, in the case of high-strength aluminum alloy represented by the 7xxx series, some studies have shown that the joint strength is only 50% to 65% of the base metal when joined by traditional fusion welding methods [40,41]. Even with laser welding, electron beam welding, laser-arc hybrid welding, etc., the joint strength can only reach ~79% [10,42,43]. The plastic deformation in the weld zone, such as rolling, can increase the joint strength by about 24% [44].…”

Effects of Different Pre-Heating Welding Methods on the Temperature Field, Residual Stress and Deformation of a Q345C Steel Butt-Welded Joint

“…Among the many factors affecting welding behavior, the structure of the pre-welding member [ 13 ], parameters of welding [ 14 ], selection of a heat source [ 15 ], welding methods and optimization [ 16 ] and the treatment method after welding [ 17 , 18 ], affect the quality of welding, the service life of a component and the safe operation of it. These factors are the guarantee of a high-performance weld and good mechanical properties [ 11 , 19 , 20 ].…”