Research On Process Optimization And Microstructure Property Of 2a97 Al-li Alloy Fiber Laser Welding

2A97 Al-Li alloy was developed independently by our country with high toughness,good thermal stability,low anisotropy and weldability,shows great potential applications in the field of advanced manufacturing.Relative to the conventional welding method,fiber laser welding has advantages of high energy density,small deformation etc.,therefore more suitable for lithium aluminium alloy plate welding.However,the research related to 2A97 Al-Li alloy fiber laser welding is not yet mature.There are less systematic study about lithium aluminium alloy laser welding's procedure-microstructure-performance,it limits the appliacation and popularization of 2A97 Al-Li alloy in the field of aerospace,aviation and armament.So carrying out the reaserch of 2A97 Al-Li alloy fiber laser welding has very important theoretical value and practical significance.In the paper,mainly studying the welding procedure,microstructure and performance of fiber laser welding joint.Preliminary analyzing the influence of welding parameters on weld formation.And according to the experiment result,welding parameters were optimized.What's more,microstructure and mechanical properties of welding joint which adopting four different types filling wire were compared.The research results providing certain reference basis on pratical appliacation about 2A97 Al-Li alloy laser welding.Acording to the systematically welding process test,the ifluence of lase welding process parameters(laser power,welding speed and wire feed rate,wire type)on joint formation were analyzed.The study found that:with the increase of the welding heat input,the welding bead width and the back-top width ratio will be improved obviously,while wire feed rate has little impact on welding bead width.The welding process parameters will be much more narrow when laser power and welding speed increasing.Under the condition of the same welding linear energy,welding forming of high speed is better.There are little possibility of cracking in welding seam using four kinds of welding wires,but exsisting hydrogen porosities sensitivity.Weld hydrogen sensitivity is arranged as follows:ER4047>ER2319?ER2A97>ER5356.By observing the 2A97 Al-Li alloy laser welding joints'microstructure characteristics shows that from welding fusion line to the center of welding seam are non-dendritic equiaxed grain zone(EQC),columnar crystal zone,columnar dendrite zone,equiaxed dendrite zone.Heat affected zone is very narrow,some coarse grain can be found out when filling ER2A97,ER2319,ER5356 wires.Non-dendritic equiaxed grain zone(EQC)of filling ER5356 is widest,and EQC of welding joints filling ER4047 is not continuous.The performance of welding joint mainly including three aspects that is micro-hardness,tensile strength and fatigue limit.The experiment results show that the difference between weld joints'hardness tat adopting four kinds of welding wire is very small,hardness decreases gradually from the base metal to the weld center,hardness of the weld center is the lowest,it is about 70 hv to 80 hv.The weld softening phenomenon is obviously.The tensile strength of the welding joint filling wire ER5356 is about 273 Mpa which can amount to 55%of the base metal.Moreover,large porosity(0.3 mm to 0.5 mm)which distribute near the fusion line has great the influence on tensile strength.The base metal tensile specimen is typical pure shear fracture,welding joint is ductile-brittle mixed fracture.Cyclic time set for 10~6,the fatigue limit of welding joint filling ER5356 wire is up to 134 mpa.It can reach 49%of tensile strength when apoting the same wire.Consider the porosity and mechanical properties of the welding joint,filling ER5356 wire is more suitable for 2A97 Al-Li alloy.