紅外線硬銲接合Ti50Ni50/純Ti或Ti-15-3合金及開發新型銅基填料之研究

Abstract

本研究利用紅外線快速加熱之特性，以BAg-8(Ag-Cu共晶)及Ticusil(Ag-Cu-Ti)兩種銀基填料硬銲異質接合Ti50Ni50形狀記憶合金與CP-Ti或Ti-15-3合金，並進行潤濕行為、顯微組織變化與接點剪力強度之研究。以BAg-8填料於850℃接合Ti50Ni50與CP-Ti時，在填料與Ti50Ni50介面處會產生CuNiTi相，銲道中央則為Ag-rich相，填料與CP-Ti介面處則會產生一系列的Cu-Ti介金屬相。破壞主要沿著銲道中央之Ag-rich相延伸，屬於延性破壞，接點剪力強度約為250MPa。而隨著持溫時間的增長，CuTi2相層逐漸增厚，使破壞形式轉變為脆性與延性混和之破壞型式，接點剪力強度也隨著持溫時間的增長而有下降之趨勢。BAg-8填料於850℃接合Ti50Ni50與Ti-15-3合金時，其顯微組織與接合Ti50Ni50與CP-Ti者差距不大，唯有在填料與Ti-15-3介面處變為含有大量V元素之單一CuTi相層，破壞也為沿著銲道中央Ag-rich相延伸之延性破壞特徵，剪力強度也約為250MPa，且不隨著持溫時間的增長而有下降之趨勢。以Ticusil填料於950℃接合Ti50Ni50與CP-Ti或Ti-15-3合金時，隨著持溫時間增長，銲道中逐漸轉變為以Ti2Ni為主相之顯微組織，破壞時沿著銲道中央之Ti2Ni相延伸，屬脆性破壞，剪力強度在200~300MPa之間。本研究同時開發三種的Cu-Mn-Ni填料接合304沃斯田鐵系不鏽鋼或是422麻田散鐵系不鏽鋼，此三種Cu-Mn-Ni填料之Cu/Mn比為共晶成分比，而Ni之添加量分別為3、5、10wt.％，研究顯示接合此兩種不鏽鋼其銲道顯微組織皆為單一(Cu,γMn)相，破壞時均由銲道中央之凝固縮孔起始，沿著(Cu,γMn)相延伸，屬延性破壞，接點剪力強度在210~280MPa之間。研究中也發現隨著填料中Ni之增加，其接合介面處之裂痕會逐漸消失，當Ni元素增至10wt.％時，於接合介面處已觀察不到裂紋。

Wetting behavior、microstructural evolution and bonding strength of infrared brazed Ti50Ni50/CP-Ti and Ti50Ni50/Ti-15-3 alloy using two Ag-based fillers are studied.For using BAg-8 filler brazed CP-Ti and Ti50Ni50, the brazed joint mainly consists of Ag-rich matrix and many interfacial layers are observed including Ti2Cu、TiCu、Ti3Cu4、TiCu4 and CuNiTi layers. The brazed joint is mainly fractured along the central Ag-rich phase in which the fracture exhibits ductile mode with the shear strength of 250MPa . Raising the brazing time will deteriorate the strength due to the fracture mode transfers to ductile/brittle mixing mode caused by the thicker interficial Ti2Cu layer. For using BAg-8 filler brazed Ti50Ni50 and Ti-15-3 alloy, microstructure is smiliar to the joint of Ti50Ni50 and cp-Ti. The only differenece is the interficial layer between Ti50Ni50 and Ti-15-3 alloy is TiCu layer. Using Ticusil infrared brazed CP-Ti(Ti-15-3) and Ti50Ni50 at 950oC, the brazed joint is full of intermetallic phases which lead the fracture mode to brittle with the shear strength of 200~300 Mpa. For infrared brazed 304 and 422 stainless steels(SS) using CuMnNi brazes, a (Cu,γMn) primary phase is found in the brazed joint. Solidification shrinkage voids are also observed in the central region of the joint and the fracture mode along these central voids is ductile with the shear strength of 210~ 280MPa. The CuMnNi brazes can effectively wet all SS at appropriate temperatures and the interfacial cracks in between braze and substrate are greatly reduced with increasing the Ni addition in CuMnNi braze.