紅外線硬銲接合Ti50Ni50形狀記憶合金與Invar合金之研究

Abstract

本研究分別使用BAg-8、Cusil-ABA及Ticusil三種銀基填料，紅外線硬銲異質接合Ti50Ni50與Invar合金，探討不同的參數下填料之潤濕行為、顯微組織演變、接點剪應力強度及破壞模式等。三種填料皆對Invar基材有良好的潤濕性，且潤濕性會隨添加Ti的含量而增加。BAg-8不與Invar反應，Cusil-ABA與Ticusil則會與Invar反應生成Ni3Ti(或CuNiTi)與Fe2Ti相。以BAg-8填料硬銲接合時，在Ti50Ni50側生成由Ni3Ti與Fe2Ti組成的介金屬相層，其餘銲道由Ag-Cu共晶組織構成，在850 oC、5分鐘時的平均剪應力值可達158MPa，在Ti50Ni50側生成脆性破壞。以Cusil-ABA及Ticusil填料硬銲接合時，從Ti50Ni50到Invar依序生成CuNiTi、Ag-Cu共晶組織、Ni3Ti(或CuNiTi)與Fe2Ti相。使用Cusil-ABA填料在850 oC、5分鐘時可得最佳之剪應力值249 MPa，而Ticusil填料在900 oC、1分鐘時的平均剪應力值可達230MPa。Cusil-ABA與Ticusil填料兩者破壞皆從Fe2Ti相起始，呈現脆性破壞形貌。本研究亦根據上述結果，使用在基材電鍍銅及雙層銀基填料等兩種方法，以改善銀基填料硬銲接合的可行性。紅外線硬銲接合Ti50Ni50/Cusil-ABA/Cu/Invar時銲道由CuNiTi、Ag-rich、CuNiTi與Cu-rich相所組成。使用雙層銀基填料的銲道顯微組織近似於單獨使用Cusil-ABA填料者，在850 oC、3分鐘時Ti50Ni50/Cusil-ABA/BAg-8/Invar接點的平均剪應力值可達212MPa。實驗結果顯示Cusil-ABA填料具有接合硬銲異質接合Ti50Ni50與Invar合金之潛力。

Interfacial reactions, microstructural evolution and shear strength of infrared brazed Ti50Ni50 and Invar joint using BAg-8, Cusil-ABA, and Ticusil filler foils have been investigated. All Ag-based fillers well wet the Invar substrate, and their wettability can be further improved by minor Ti addition. The brazed joint using BAg-8 is comprised of Ag-Cu eutectic. There is no interfacial reaction layer between BAg-8 braze and Invar substrate. However, Fe2Ti and Ni3Ti intermetallic compounds are observed close to Ti50Ni50 substrate. Average shear strength of Ti50Ni50/ BAg-8/Invar joint brazed at 850 oC for 300 s is 158 MPa. The joint is fractured along the interface close to Ti50Ni50 substrate, and fractograph is featured with cleavage dominated fracture. For Cusil-ABA and Ticusil brazed joints, the sequence of identified phases from Ti50Ni50 to Invar substrate is CuNiTi, Ag-Cu eutectic and mixture of Fe2Ti and Ni3Ti. The specimen brazed at 850 oC for 300 s using Cusil-ABA filler demonstrates the best average shear strength of 249 MPa. The average shear strength of Ti50Ni50/Ticusil/Invar joint brazed at 900 oC for 60 s is 230 MPa. Cracks are initiated from Fe2Ti phase for both Cusil-ABA and Ticusil brazed joints, and their fractographs are dominated by quasi-cleavage fracture. Two modified approaches of infrared brazed Ti50Ni50 and Invar joints using the Cusil-ABA braze are also investigated. For Cu electroplated Invar substrate, the brazed Ti50Ni50/Cusil- ABA/Cu/Invar joint is comprised of CuNiTi, Ag-rich and Cu-rich phases. For the dual filler foils method, the microstructure of brazed Ti50Ni50/Cusil-ABA/BAg-8/Invar joint is similar to that of Ti50Ni50/Cusil-ABA/Invar joint with shear strength of 212 MPa. Based on the experimental observation, the Cusil-ABA foil shows the potential in brazing Ti50Ni50 and Invar substrates.