Abstract
Electron beam welding of a titanium alloy (Ti-6Al-4V) and a kovar alloy (Fe-29Ni-17Co) was performed by using a Cu/Nb multi-interlayer between them. Microstructure and composition of welded joints were analyzed by means of optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Mechanical properties of welded joints were evaluated by microhardness and tensile strength tests. Results indicated that in case of 0.22 mm thickness of Nb foil, microstructure of the titanium alloy side was mainly composed of Ti solid solution and some intermetallic compounds such as FeTi and CuTi2, whereas in case of 0.40 mm thickness of Nb foil, the appearance of weld was more uniform and hardness of the weld zone decreased sharply. However, tensile strength of welded joints was increased from 88.1 MPa for the 0.22 mm Nb foil to 150 MPa for the 0.40 mm Nb foil. It was found that thicker Nb foil could inhibit diffusion of Fe atoms towards the titanium alloy side, thus promoting the formation of Ti solid solution and a small amount of CuTi2 and eliminating FeTi. In addition, in both cases, Cu0.5Fe0.5Ti was found in the fusion zone of the titanium alloy side, which had an adverse effect on mechanical properties of welded joints.
Highlights
Titanium alloys are widely used in nuclear, aerospace, and chemical industries because of their high corrosion resistance, light weight, high specific strength, and other hightemperature properties [1]
Our work demonstrated that the electron beam welding method can be used effectively to control the formation of brittle intermetallic compounds (IMCs), improving the joint quality and mechanical properties
It was found that large energy input led to excessive expansion of metals, and cracks were formed during its cooling. e residual stress, generated at the interface, can result in a reduction of properties of the welded joints due to the di erent coefficient of thermal expansion (CTE) between copper and kovar alloy
Summary
Titanium alloys are widely used in nuclear, aerospace, and chemical industries because of their high corrosion resistance, light weight, high specific strength, and other hightemperature properties [1]. Joining titanium and kovar alloys can achieve a combination of their advantages to improve performance of products to meet the needs for aerospace and electronic packaging applications [4, 5]. Kundu et al [9] showed that when titanium was diffusion bonded to a 17-4PH stainless steel, FeTi and Fe2Ti were produced. Chen et al [11] joined 201 stainless steel and TC4 titanium alloy by laser welding. It was found that if the laser beam was offset on the side of titanium alloy, more intermetallic compounds (IMCs) and cracks were produced. According to these research results, it appears that the challenge in connecting titanium and kovar alloys is the formation of brittle IMCs (Fe2Ti and FeTi)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
