【作者】 黄亮；

【导师】 杜学铭； 姚伟； 杨璟；

【作者基本信息】 武汉理工大学 ， 材料加工工程， 2014， 硕士

【摘要】 钛合金具有密度小、比强度高、耐腐蚀性能好等优良的特性，因此它广泛应用于航空航天制造领域。常用的钛合金连接方法有铆接和焊接两种，相比而言，焊接具有减轻结构重量，提高结构性能的优点。而在众多钛合金焊接方法之中，激光焊接以其优异的特性弥补了传统焊接方式热源发散、能量密度小、焊接速度低、接头性能差及结构变形量大的缺点，使焊缝成形更好、生产效率更高，同时变形量也更小，更符合工业生产的要求。本文采用YAG激光器对TC4钛合金激光焊接工艺进行了研究，并制成了壁板模拟件，同时对接头及模拟件的焊接残余应力进行了测试、分析和消除实验。对促进壁板构件工程应用有着积极的作用。本文通过对2mm厚TC4钛合金薄板进行激光焊接，分析了不同工艺参数下焊接接头（包括对接接头和T型接头）的成型、内外部质量及显微组织特性，并对其室温下的静力学性能进行了测试。研究结果表明：对于对接接头而言，当功率一定时，焊接速度越小则焊缝两面的熔宽越宽；较大的功率的激光焊接更有利于减少气孔的产生；较大的焊接速度会导致更小的热影响区，有利于提高焊缝的质量。对于T型接头而言，功率一定时，较小的焊接速度导致较大的熔深，更有利于焊缝的融合；而送丝速度为3.5m/min时，熔深和焊脚高度最大，随着送丝速度的增大和减小均会导致熔深和焊脚高度的减小。对接和T型接头进行微观组织、显微硬度和力学性能进行分析和对比，可以发现，接头的显微硬度、抗拉强度和屈服强度均要高于母材，但塑性比母材略低。这种情况主要是由于接头各区域的显微组织成分和分布不同所造成的。尝试采用了机械应变法以及在机械应变法基础上改进而成的图像定位法分别对对接和T型接头进行了残余应力测试，并得到了较理想的结果，获得了TC4钛合金YAG激光焊接残余应力峰值及分布规律。发现了线能量对残余应力的影响，当线能量较大时，其残余应力峰值也相应较大且拉应力区域较宽，当线能量为70kJ/m时，残余应力达到了测量的峰值604.76MPa，约为母材屈服强度的2/3。通过对比，选择了适当的工艺制成了壁板模拟件，并采用X射线衍射法对模拟件分区域进行了残余应力测试，获得了残余应力的峰值及分布规律。T型接头和对接接头的峰值残余应力分别为488.01MPa和674MPa，约为母材屈服强度的50%-70%。采用了热处理方法进行消应力处理，消应力效果明显，峰值残余应力分别降至39MPa和171MPa，为母材屈服强度的4%-17%。更多还原

【Abstract】 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.更多还原