【作者】 陈岩；

【导师】 何鹏；

【作者基本信息】 哈尔滨工业大学 ， 材料工程（专业学位）， 2019， 硕士

【摘要】 Ti₂AlNb合金作为镍基高温合金的替代材料之一,其应用过程中不可避免涉及到Ti₂AlNb合金与镍基高温合金的连接问题,但钛合金与镍合金直接焊接时钛镍化合物的生成往往会使接头的性能大大降低;与此同时,镍基高温合金钎焊时所用的常规镍基钎料的熔化温度超过了Ti₂AlNb合金的相变温度（950℃）,在直接钎焊时会引起Tiz Al Nb合金相变。本文针对TizAlNb合金于镍基高温合金的连接问题,使用添加阻隔层与分步钎焊的方式,将Ti₂AlNb合金与镍基高温合金（GH536）的钎焊拆分为两步,先将镍基合金与阻隔层Nb在Ti₂AlNb合金相变点以上焊接,然后将半成品在Ti₂AlNb合金相变点以下与Ti₂AlNb进行钎焊,不但避开钛和镍直接接触,而且避开了Ti₂AlNb合金相变。本文使用BNi-2钎料对镍基/Nb进行了钎焊,使用TiZrNiCu钎料对Ti₂AlNb/Nb进行了钎焊,优化出分步钎焊两侧的最优参数,并最终完成了Ti₂AlNb合金与GH536镍基高温合金的分步钎焊,对接头界面组织与性能进行了分析,探究了焊接工艺参数与接头组织与性能之间的关系。根据研究表明,使用BNi-2钎焊GH536镍基高温合金与Nb时,接头结合良好,焊缝主要组成相分别是（Nb）ss、Ni6Nb7、Nis Nb、SNb、Nb-Ni-Si化合物和（Ni）ss。当钎焊温度为1050℃、保温时间为l Omin时,接头强度最大,达到265.1MPa,断裂位置发生在脆性相Ni3Nb处,该相为接头的薄弱区域。采用TiZrNiCu钎料对Ti₂AlNb与Nb进行钎焊接头结合良好,焊缝主要是由（Ti,Nb）ss、Cu Niz Ti、（Ti,Zr）ss、（Ti）ss组成。当钎焊温度为900℃、保温时间为10min时,接头强度最大,达到110.1MPa,断裂位置发生在脆性相Cu Niz Ti处,该相为脆性相,削弱了焊接接头,该处为接头的薄弱区域。采用分步钎焊可以得到良好的钎焊接头,对比直接使用TiZrNiCu和BNi-2钎料进行钎焊剪切强度分别提高了404.9%与185.7%。在向TiZrNiCu钎料中加入15%的Ti（wt.%）后,接头中黑色块状的CuNi₂Ti消失,该位置生成了（Ti,Zr）₂（Ni,Cu）,焊缝界面组织得到改善,该方法使焊缝的剪切强度提高了36.8%。更多还原

【Abstract】 As an alternative material to nickel-based super alloys,Ti₂AlNb alloy inevitably involves the joining of Ti₂AlNb alloy and nickel-based super alloy in its application.However,the formation of titanium-nickel compound in the direct welding of titanium alloy and nickel alloy tends to make the joint Greatly reduced performance.At the same time,the melting temperature of the conventional nickel-based solder used in the brazing of nickel-based super alloys exceeds the phase transition point of the Ti₂AlNb alloy,which will cause the phase change of Ti₂AlNb alloy during direct brazing.In this paper,the brazing of Ti₂AlNb alloy and nickel-base super alloy（GH536）is divided into two steps by adding barrier layer and step brazing for the connection of Ti₂AlNb alloy to nickel-base super alloy.Firstly,the GH536 alloy and the barrier layer Nb are welded above the phase transition point of the Ti₂AlNb alloy,and then the semi-finished product is brazed with Ti₂AlNb below the phase transition point of the Ti₂AlNb alloy,which not only avoids the direct contact of the titanium-nickel,but also avoids the phase change of the Ti₂AlNb alloy.In this study,GH536 alloy and Nb were brazed with BNi-2 solder.Ti₂AlNb and Nb were brazed with Scrutinize solder to optimize the optimal parameters on both sides of step-by-step soldering.Finally,Ti₂AlNb alloy was completed.Step soldering of GH536 nickel-base super alloy.In this study,various analytic test methods were used to analyze the interface infrastructure and properties by scanning electron microscopy（SEM）,energy spectrum analysis（EDS）and X-ray diffraction analysis（XRD）.The welding process parameters and joints were explored.The relationship between organization and performance.According to the research,when the BNi-2 brazing GH536 nickel-base superalloy and Nb are used,the joints are well bonded.The main constituent phases of the weld are（Nb）ss,Ni₆Nb₇,Ni₃Nb,Cr₂Nb,Nb-Ni-Si compounds and（Ni）ss.When the brazing temperature is 1050 ℃ and the holding time is 10 min,the joint strength is the largest,reaching 265.1MPa,and the fracture position occurs at the brittle phase Cr₂Nb,which is the weak region of the joint.The TiZrNiCu solder is used to bond the Ti₂AlNb and Nb brazed joints.The weld is mainly composed of（Ti,Nb）ss,Cu Ni2 Ti,（Ti,Zr）ss and（Ti）ss.When the brazing temperature is 900 ℃ and the holding time is 10 min,the joint strength is the largest,reaching 110.1MPa,and the fracture position occurs at the brittle phase CuNi₂Ti,which is a brittle phase,which weakens the welded joint,which is a weak area of the joint.A good brazed joint can be obtained by step brazing.The brazing shear strength of the TiZrNiCu and BNi-2 brazing materials is improved by 404.9% and 185.7%,respectively.After adding 15% Ti（wt.%）to the TiZrNiCu solder,the black block CuNi₂Ti disappeared in the joint,and（Ti,Zr）₂（Ni,Cu）was formed in this position,which increased the shear strength of the joint by 36.8%.更多还原