鈦鎳形狀記憶合金紅外線硬銲接合之研究

The Study of Infrared Brazing Ti50Ni50 Shape Memory Alloy

薛人豪(Ren-Haur Shiue)

指導教授 ： 吳錫侃

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2006年)

https://doi.org/10.6342/NTU.2006.00569

摘要

紅外線硬銲接合Ti50Ni50同質及異質合金，首先接合Ti50Ni50及Ti-6Al-4V合金以BAg-8為填料，顯示其對Ti-6Al-4V基材有極佳潤濕性，惟對Ti50Ni50基材則無潤濕性。於硬銲中大量的Ti由Ti-6Al-4V基材溶入填料，顯著提昇填料與Ti50Ni50合金的潤濕性，有助於接合Ti50Ni50及Ti-6Al-4V合金。在850oC硬銲下，填料區主要為Ag-Cu亞共晶組織，Ag並不與基材反應，Cu與Ti-6Al-4V側激烈反應生成TiCu4、Ti3Cu4、TiCu及Ti2Cu等相；在Ti50Ni50側則生成CuNiTi相。剪力試驗得知，平均剪應力值約為200 MPa；其中CuNiTi相的生成雖提高潤濕性，但卻造成接合界面破壞的主因。本研究同時選用兩種不同含Ti量之Ag-Cu-Ti活性填料接合Ti50Ni50合金，研究結果顯Ti50Ni50/Cusil-ABA®/ Ti50Ni50界面反應，主要包括Cu-rich，Ag-rich和CuNiTi相；而Ti50Ni50/Ticusil®/Ti50Ni50者，因填料之含Ti量較高，界面反應較為激烈，導致填料中Cu因與基材反應而消耗，並於界面生成TiCu2相。彎曲試驗說明TiCu2界面相，對於形狀記憶性質的減損少於CuNiTi相。使用兩種填料之剪力強度均能超過200MPa，惟CuNiTi及TiCu2界面相的存在均不利於剪力强度。本研究也使用Au-20Cu及Au兩種填料紅外線硬銲接合Ti50Ni50合金。Au-20Cu硬銲區主要生成AuCu、Au2NiTi及Ni3Ti相；Au者是Au4Ti及Au-rich相。彎曲試驗結果顯示使用Au填料之形狀記憶性質優於Au-20Cu填料，且與Ti50Ni50母材之形狀記憶性質相同。

關鍵字

Ti50Ni50 ； Ti-6Al-4V ； 紅外線硬銲接合 ； BAg-8 ； 形狀記憶性質 ； 界面顯微組織演化 ； 剪力強度

並列摘要

The study comprises the dissimilar or similar joining of Ti50Ni50 SMA by infrared brazed. Microstructure evolution, reaction path and shear strength of infrared brazed Ti50Ni50 and Ti-6Al-4V joints using BAg-8 braze alloy have been investigated. The braze alloy can readily wet on Ti-6Al-4V, but not on Ti50Ni50. Titanium dissolves from Ti-6Al-4V to enhance the wettability of braze alloy on Ti50Ni50 during brazing. The joint is mainly comprised of hypoeutectic silver and copper for specimen infrared brazed below 850oC. The silver does not react with both substrates. The copper is readily reacted with titanium vigorously to form TiCu4, Ti3Cu4, TiCu and Ti2Cu phases in Ti-6Al-4V side and form CuNiTi phase in Ti50Ni50 side. The average shear strength of the specimens infrared brazed below 850oC is about 200 MPa. Although the presence of interfacial CuNiTi phase is beneficial to the wettability of molten braze alloy on Ti50Ni50 substrate, it is detrimental to the bonding strength of the infrared brazed Ti50Ni50/BAg-8/Ti-6Al-4V joint. The infrared brazed Ti50Ni50 alloy using Cusil-ABA® and Ticusil® active braze alloys are also investigated. The Ag-Cu eutectic braze alloy can readily wet Ti50Ni50 substrate by minor titanium addition. The brazed Ti50Ni50/Cusil-ABA®/Ti50Ni50 joint is mainly comprised of Cu-rich, Ag-rich and CuNiTi phases. However, the brazed Ti50Ni50/Ticusil®/Ti50Ni50 joint causes more vigorous reaction between filler metal and substrate, resulting in the exhaustion of copper from the molten braze, and forming TiCu2 interfacial layer confirmed by EPMA and XRD tests. The TiCu2 phase is less detrimental to the shape memory effect than CuNiTi phase during the shape recovery bending test. Shear strength of brazed joints exceeds 200MPa for both braze alloys if the brazing time exceeds 180 seconds. However, thick interfacial CuNiTi and TiCu2 layers can deteriorate the shear strength. Infrared brazing Ti50Ni50 shape memory alloy using pure Au and Au-20Cu has been evaluated. Based on the bending test results, the shape memory effect of brazed joint using Au filler metal is superior to that using Au-20Cu braze alloy. The shape recovery ratio of the joint using Au filler is identical to that of Ti50Ni50 substrate, and there is no crack on the brazed joint after bending test. Consequently, the pure Au filler metal demonstrates the potential application in brazing Ti50Ni50 shape memory alloy.

並列關鍵字

Ti50Ni50 alloy ； Ti-6Al-4V ； infrared brazing ； BAg-8 ； shape memory effect ； microstructural evolution ； shear strength

參考文獻

1)T. B. Massalski: Binary Alloy Phase Diagrams, (ASM International, Metals Park, 1990).

2)S. Miyazaki, K. Otsuka and Y. Suzuki: Scripta Metall. 15 (1981) 287.

4)S. Miyazaki, T. Imai, Y. Igo and K. Otsuka: Metall. Trans. 17A (1986) 115.

5)K. Otsuka, K. Shimizu, Int. Met. Rev. 31 (1986) 93.

6)H. C. Lin and S. K. Wu: Acta Metall. 42 (1994) 1623.