紅外線硬銲接合Ti50Ni50形狀記憶合金與316L不鏽鋼/Inconel 600合金之研究

Abstract

本研究使用Cu作為擴散阻絕層之三層填料(BAg-8/Cu/Cusil-ABA) 紅外線硬銲異質接合Ti50Ni50與316L不鏽鋼，以及使用BAg-8、Cusil-ABA及Ticusil三種銀基填料紅外線硬銲異質接合Ti50Ni50與Inconel(In) 600合金，探討在不同的參數下填料對基材之潤濕行為、顯微組織演化、銲點剪應力強度及破壞模式等。接合Ti50Ni50/Cusil-ABA/Cu/BAg-8/316L時，銲道由(CuxNi1-x)2Ti、Cu-rich、純Cu以及Ag-Cu共晶組織所組成；當銅箔厚度為70μm時，最佳條件在820℃×5min，剪應力強度有292MPa，破壞位置於Ag-Cu共晶組織與316L的交界處，屬於延脆混合破壞；當銅箔厚度為50μm時，在850℃×5min下，其剪應力強度達349MPa，且為延脆混合破壞；但當銅箔厚度為25μm時，銅箔失去了阻絕能力，Ti-Fe介金屬相生成，銲道由(CuxNi1-x)2Ti、Cu-rich、Ag-Cu共晶組織和Ti(Fe,Ni)所組成，其剪應力強度最佳為236MPa。Bag-8無法有效潤濕In 600合金但Cusil-ABA與Ticusil因含有Ti而有較好的潤濕效果；接合Ti50Ni50/BAg-8/In 600時，銲道由Ni3Ti相，Ag-Cu共晶及Cu-rich組成，因脆性相Ni3Ti生成以及潤濕性差，使剪應力強度不佳，最好僅有72±32MPa，破壞發生於Ni3Ti相，形態以脆性破壞為主；使用Cusil-ABA接合時銲道依序為CuNiTi相、Ag-Cu共晶區域、CuNiTi相、Ni3Ti相，在900℃×5min時有最佳的剪應力強度，平均有324MPa，破壞主要發生在Ag-Cu共晶區且為延脆混合破壞；使用Ticusil時有類似Cusil-ABA的銲道組織，但在In 600端有明顯的Ag、Cu滲入基材的情形發生，且在填料與基材間有析出Cr-Fe固溶體；在950℃×3min時剪應力強度達到最高，平均有300MPa，以延脆混合破壞為主。

BAg-8, Cusil-ABA, Ticusil, and Copper fillers are used to infrared braze Ti50Ni50 and two other alloys, 316L stainless steel(SS) and Inconel (IN) 600. The brazed joint’s interfacial reaction, microstructure evolution and shear strength are investigated. Cu film is used as a diffusion barrier in the filler with three layers (BAg-8/Cu/Cusil-ABA) to prevent the formation of brittle Fe-Ti intermetallics in TiNi/316L joint. For TiNi/ BAg-8/Cu/Cusil-ABA /316L joint, it is composed of (CuxNi1-x)2Ti, Cu-rich, Cu, and Ag-Cu eutectic. When the thickness of cu film is 70μm, the shear strength is 292MPa for the joint brazed at 820℃×5min. If the Cu film thickness reduces to 50μm, the joint’s shear strength can reach 349 MPa when it is brazed at 850℃×5min. However, when thickness is reduced to 25μm, it can not prevent the formation of brittle Fe-Ti intermetallics and the shear strength reduces to 236 MPa. For IN600, the wettability of BAg-8 is degraded by surface CrxOy oxides, but the Ti in Cusil-ABA/Ticusil can improve the wettability significantly. TiNi/Bag-8/IN600 joint is composed of Ni3Ti, Ag-Cu eutectic and Cu-rich, and has the average shear strength of 72MPa when it is brazed at 850℃×5min. This joint is fractured along Ni3Ti. For Cusil-ABA and Ticusil brazed joints, the sequence of identified phases from TiNi to IN600 is CuNiTi, Ag-Cu eutectic and the mixture of CuNiTi and Ni3Ti. The specimen brazed at 900℃×5min using Cusil-ABA filler demonstrates the best shear strength of 324 MPa. The shear strength of TiNi/Ticusil/IN600 joint brazed at 950℃×3min is 300 MPa. When the brazing time increases, the shear strength of the jonit used Ticusil filler decreases due to the growth of Ni3Ti intermetallics in which cracks are initiated from Ni3Ti and the fractograph is dominated by quasi-cleavage fracture.