Characterization of Laser-Welded Ti Alloy and Stainless Steel Joint Using Cu Interlayer
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JMEPEG https://doi.org/10.1007/s11665-019-04319-1
Characterization of Laser-Welded Ti Alloy and Stainless Steel Joint Using Cu Interlayer Yan Zhang, DaQian Sun, XiaoYan Gu, and HongMei Li (Submitted June 4, 2018; in revised form September 4, 2019) In this study, Cu was used as an interlayer to restrain the formation of brittle Ti-Fe intermetallics when joining Ti alloy to SS. Microstructures of the joint were analyzed using optical microscopy, scanning electron microscopy and x-ray diffraction. Besides, the tensile strength of the joint was also measured. The melting amount of base materials was controlled by changing thickness of Cu interlayer to control the melting proportion in weld. The melting amount of base materials in weld decreased with the thickness of Cu interlayer. The content of Cu solid solution in weld increased with the thickness of Cu interlayer. Ti-Cu compound layer was formed on the Ti alloy side. The width of the Ti-Cu compound layer increased with the increase in heat input. The tensile strength of joint was largely impacted by Ti-Cu compound layer. The tensile strength of joint first increased and then decreased with the increase in width of the Ti-Cu compound layer. Keywords
laser welding, mechanical property, microstructure, SUS301L stainless steel, TC4 Ti alloy
1. Introduction Titanium (Ti) and its alloys are broadly applied in aerospace industry as characterized by high strength, good toughness and good fatigue resistance. Yet the application of Ti alloy has been limited by its high cost, poor weldability and processability (Ref 1). Thus far, stainless steel (abbreviated as SS) has been the most commonly applied structural material. Such SS has plenty of excellent performances, such as weldability, processability and mechanical properties, as well as the relatively low cost (Ref 2). If the Ti alloy is welded to SS, the welded structure will combine the advantaged performances of the two materials and reduce the cost. Actually, the direct fusion welding of Ti alloy and SS could readily produce numerous TiFe intermetallics by welding. These Ti-Fe intermetallics are highly brittle, which makes the conventional welded joints cracked spontaneously under large residual stress between the Ti alloy and SS (Ref 3, 4). Thus, restraining the formation of brittle Ti-Fe intermetallics in weld is critical for building the reliable connection between Ti alloy and SS. The interlayers, inclusive of Cu (Ref 5), Ag (Ref 6), Ni (Ref 7), Al (Ref 8) and Mg (Ref 9), have been adopted to restrain the formation of TiFe intermetallics in the course of welding. The most widely used interlayers are Cu and their alloys since Cu does not produce brittle intermetallics with iron, chromium, nickel and carbon. It is proved by comparative analysis that Cu in the noted interlayers has the best welding effect. Cu has better Yan Zhang, School of Mechanical Engineering, Xinjiang University, Wulumuqi 830000, China; and DaQian Sun, XiaoYan Gu, and HongMei Li, Key Laboratory of Automobile Materials, School of Materials Science a
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