Research On Laser Welding Of High Strength Aluminum In T-jiont

High strength aluminum alloy is one of the most important materials and finds extensive application in aerospace industry because of its light weight, superior strength-to-weight ratio, and high elastic modulus. Laser welding with high energy density can offer remarkable advantages over conventional fusion welding processes, such as minimal component distortion and high productivity, and is specifically suitable for joining aerospace structures. It is prominent to reduce weight that using welding crafts replace traditional rivet bond especially in the manufacturing of the aircraft skin, panel etc…However, due to the properties of aluminum alloy and the structural characteristics of T-joint, whether traditional TIG welding or advanced laser welding has to face with some problems in formation of weld, such as pores, cracks, deformation, which are difficult to solve by single way. In this paper, the fillet weld for T-joint of 3.0 mm thick 5A90 Al-Li alloy has been completed through laser welding with filling wire on the base of laser welding, which provides many advantages which are not found in either.First of all, the position device, wire feeder and fixture which offer the equipment condition for craft investigation have been designed and optimized according to requirements of laser welding with filling wire tests and structural characteristics of T-joint.In addition, the influences of welding parameters on fillet weld formation were investigated based on orthogonal tests. The results showed that the main factors affecting weld formation are welding angle and displace. With the results of orthogonal tests, laser-beam-welded T-joint parameter of SUS304 stainless steel was optimized, and the rules of parameters selection were set up. The optimal weld formation was obtained from validating trial. The laser welding with filling wire for T-joints of Al-Li alloy were carried out based on optimized parameters of laser welding, the results shows that the weld formation was improved greatly and hot cracks were avoided.Finally, the influences of the pores for T-joint have been studied. Microstructures and mechanical properties of weld have been studied and analyzed as well. The results show that laser welding with filling wire in T-joint can complete good formations of weld which has similar organizations on both sides and has properties of grain-based and transition uniform. the tensile strength of joint with filling wire is increased nearly 20% than the joint by laser welding. Besides, the microhardness of Al-Li alloy weld bead is tended toward uniform and also affected by the welding sequence. The porosity and micro structure defect vanishes after heat-treatment technology at the cost of hardness decreases of the weld center.The research results can help to advance the development and application of laser welding in T-joint, as well as provides a reference for eliminating the porosity in weld bead after welding. The results have also formed the basis of dual beam laser welding of T-joint for later studies.