The Technology And Residual Stress Analysis Of Laser Welding Of TC4Titanium Alloy

Tianium alloy has low density,high strength-to-weight ratio and superiorcorrosion resistance,so it has been widely used in aircraft and spacecraft industry.Themost common ways of tianium alloy connection are riveting and welding.Comparewith riveting,welding can reduce the weight of structure and improve the preformanceof structrue.Of the many ways of welding,laser welding is better than others,it madeup the disadvantage of traditional welding such as heat dissipation,low energydensity,low welding speed,poor property of joint and huge deflection.So laserwelding can meet the requirements of industrial manufacture well.Differentperformance of different parametres of YAG laser beam welding of TC4titaniumalloy has been researched,and aircraft panel simulator has been produced.Appropriateways has been used to test and eliminate the residual stress of joint and panelsimulator.That’s positive for industry manufacture of aircraft panel.2mm thick TC4panel has been used in laser weldingexperiment.molding,Internal and external quality,microscopic structure andmechanical property of different laser welding technological parametres hasanalysed.The results prove that for butt joint when the power is constant,lowerwelding speed causes wider welding,and higher power leads to less porosity.ForT-butt when wire feed rate is3.5m/min,penetration and fillet weld size aremaximized.The results also shows the microhardness,tensile strength and yieldstrength of butt are higher than base metal.Beacause the microscopic structure in buttis different from base metal.Image position method has been invented and used in residual stressmeasurement with mechanical strain gage.Residual stress of YAG laser welding ofTC4titanium alloy has been obtained.The research results shows the higher heatinput leads to higher peak residual stress and wider tensile stress area.when heat inputis70kJ·m-1,the peak value of lengthways residusdual stress is604.76MPa,about2/3times yield strength of base metal.Imitation item of aircraft panel has been made with appropriate parameters.With XRD method,the peak value and distribution rule of residual stess of the imitationitem has been obtained.The peak value of T-butt is488.01MPa as well as thebutt-joint is674MPa,about50%to70%times yield strength of base metal.Heattreatment has been used in stress elimination,and the results of residual stressdecrease are remarkable,the peak value reduced to39MPa和171MPa,about4%to17%times yield strength of base metal.