Influence of Welding Speed on the Microstructure and Mechanical Properties of Electron Beam-Welded Joints of TC4 and 4J29 Sheets using Cu/Nb Multi-Interlayers

Abstract

Dissimilar metal joining between titanium and kovar alloys was conducted using electron beam welding. Metallurgical bonding of titanium alloys and kovar alloys was achieved by using a Cu/Nb multi-interlayer. The effects of welding speed on weld appearance, microstructure and mechanical properties of welded joints were investigated. The microstructure of welded joints was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The mechanical properties of welded joints were investigated by tensile strength and micro-hardness tests. The results showed that welding speed had great effects on the weld appearance, microstructure, and mechanical properties of electron beam-welded joints. With an increase of welding speed, at the titanium alloy side, the amount of (Nb,Ti) solid solution was increased, while the formation of brittle FeTi was effectively suppressed. At the kovar alloy side, microstructure was mainly composed of soft Cu solid solution and some α-Fe + γ phases. In addition, higher welding speeds within a certain range was beneficial for eliminating the formation of cracks, and inhibiting the embrittlement of welded joints. Therefore, the tensile strength of welded joints was increased to about 120 MPa for a welding speed of 10 mm/s. Furthermore, the bonding mechanism of TC4/Nb/Cu/4J29 dissimilar welded joints had been investigated and detailed.

Obtaining of combined titanium-steel structures by electron beam freeform fabrication using niobium and copper interlayers

“…Considering that niobium is not metallurgically compatible with iron, it is essential to use the second interlayer, namely nickel [17,[26][27][28][29][30][31], copper [2, 6, 8,9, 16,19,[21][22][23] or alloys based on them. Based on the analysis of the nickel interaction with vanadium [26,27, 28] and niobium [17,[29][30][31] the formation of brittle phases is noted in both systems [26,[29][30][31].…”

“…It`s implementation makes it possible to increase the installation and repair work manufacturability. Refractory metals such as vanadium [8][9][10][11][12][13][14], niobium [15][16][17][18][19][20][21][22][23] and tantalum [10,15,24,25] can be used for deposition on titanium alloy during additive forming. However, the use of tantalum may cause technological problems due to the large difference in melting temperatures.…”

“…At the same time, the titanium enriched zones ful l the conditions for the formation of the ω-phase. Taking into account the terms of the titanium interaction with refractory metals, the use of a niobium interlayer is preferable.Considering that niobium is not metallurgically compatible with iron, it is essential to use the second interlayer, namely nickel [17,[26][27][28][29][30][31], copper [2, 6, 8,9, 16,19,[21][22][23] or alloys based on them. Based on the analysis of the nickel interaction with vanadium [26,27, 28] and niobium [17,[29][30][31] the formation of brittle phases is noted in both systems [26,[29][30][31].…”

Realization of Enhanced Mechanical Properties of Solid-State Welded Ti Alloy with Commercial Purity

“…However, due to the occurrence of oxidation and intermetallic compounds such as TiO 2 and TiAl during the fusion welding, it is difficult to obtain the enough mechanical properties such as microhardness and yield and tensile strengths [3]. For example, when joining Ti alloys by the conventional fusion welding such as gas tungsten arc welding (GTAW), laser welding (LW) and electron beam welding (EBW), the welds gives rise to formation of brittle intermetallic compounds (IMCs) in the welded area, resulting in loss in strength of the joint [4,5].…”

Powder interlayer bonding of titanium alloys: Ti-6Al-2Sn-4Zr-6Mo and Ti-6Al-4V

“…A nickelbased superalloy and TiAl alloys have been successfully laser welded by utilising vanadium and copper composite interlayers [27]-the interlayer again helping to reduce the formation of brittle intermetallics and improving joint strength. Interlayers have also been used in combination with electron beam welding, where niobium and copper interlayers have been used to facilitate the bonding of titanium and kovar alloys [28].…”