Research On ZrO₂/Ti-6Al-4V Brazed Joints Using Active Ag-Cu-Ti Brazing Filler And Amorphous Ti-Zr-Cu Brazing Filler

With the rapidly development of building industry and new technology, people will paymore attention to the quality and property of welding structures. Ceramic material and metalmaterial both display excellent performances. The successful connection of two materialscan make their advantages play to the maximum effectiveness. Therefore, the connection ofmetal and ceramic materials has a wide representativeness. There are many ways to connectmetal and ceramic. Brazing process has unique advantages which widely applied in themetal/ceramic brazed joint. The traditional brazing material is Ag–Cu–Ti filler whichcontains the precious metal Ag. It is also increasing the cost in practice. In order to reducethe cost, people need to develop a new kind of solder to replace expensive Ag-based solder.In recent years, many scholars research on metal/ceramic brazed joints using Ag-basedbrazing filler, and discuss the problems that exist in the brazing process. However, there aresome divergences in reported literatures, and it does not come to an agreement so far. In thispaper, we use self-made active Ag–Cu–Ti brazing filler and amorphous Ti–Zr–Cu brazingfiller to braze ZrO₂/Ti–6Al–4V, and explain the different phenomenon. The main conclusionsare given as follows.1. Ag–Cu–Ti/ZrO₂system and Ti–Zr–Cu/ZrO₂system both belong to the reactivitywetting, but the wetting behavior are different. In the Ag–Cu–Ti/ZrO₂system, the wettingspread is mainly controlled by the interfacial reaction products. Active element Ti gathers atthe ZrO₂interface and reacts with ZrO₂. The reaction products are TiO, Cu3Ti3O and Cu–Tiintermetallic compounds. Cu3Ti3O which has the nature of the metal plays an important rolein the spread of wetting. In the Ti–Zr–Cu/ZrO₂system, the reaction products are TiO,Cu3Ti3O and （Ti, Zr）2Cu also, but the wetting spread is mainly controlled by the propertiesof Ti–Zr–Cu alloy. As the temperature increasing, the viscosity of the alloy decreases, whichis helpful for melting alloy spreading. However, the releasing of O from ZrO₂substratehinders the spreading.2. Brazing holding time has a little effect on ZrO₂/Ag–Cu–Ti/Ti–6Al–4V brazed jointsat850oC. The structure of interface is ZrO₂/TiO/Cu2Ti4O/Ag-rich phase/Cu–Tiphase/Ti–6Al–4V alloy. The shear strength of joints is mainly affected by the reactionproducts TiO and Cu2Ti4O, holding time has less effect on it. When the brazing temperatureexceeds900oC, the structure of interface converted to ZrO₂/TiO/Cu–Ti phase/Ti–6Al–4Valloy. Brazing temperature has a great effect on the interface structure. The TiO layer turnsthicker with increasing temperature, which has negative effects on shear strength obviously.Brazing cooling rate has a little effect on interface structure of joints, but it can increase theresidual stress of welding seam, which effect on the shear strength of brazed joints.Researching on ZrO₂/Ti–6Al–4V brazed joints using active Ag–Cu–4wt.%Ti brazing filler gets the best process parameters: brazing temperature is850oC; holding time is10min;cooling rate is5oC/min; the maximum shear strength is up to178MPa.3. As to ZrO₂/Ti–Zr–Cu/Ti–6Al–4V brazed joints, the structure of interface is ZrO₂/（Ti,Zr）2Cu/Cu2Ti4O/TiO/residual solder phase/Cu–Ti phase/Ti–6Al–4V alloy. With temperatureincreasing, the structure of interface becomes ZrO₂/Cu2Ti4O/TiO/Cu–Ti phase/Ti–6Al–4Valloy. Brazing holding time and brazing temperature are mainly effect on the thickness ofTiO layer. The shear strength of the brazed joints is controlled by the thickness of TiO layer.The longer the holding time and the higher the brazing temperature is, the lower the shearstrength of the joint is. The cooling rate mainly effects on the residual stress of the joint. Thefaster the cooling and the greater the joint weld residual stress is, the lower the shear strengthis. Researching on ZrO₂/Ti–6Al–4V brazed joints using amorphous Ti–Zr–Cu brazing fillergets the best process parameters: brazing temperature is900oC; holding time is10min;cooling rate is5oC/min; the maximum shear strength is up to162MPa.In conclusion, this study not only contributes to our understanding of the traditionalactive Ag–Cu–Ti brazing filler, but also provides useful information and positive guidancefor the development of novel brazing filler.