Weld Formation Mechanism and Microstructural Evolution of TC4/304 Stainless Steel Joint with Cu-Based Filler Wire and Preheating

Abstract

Ti-Fe intermetallic compounds were effectively suppressed with Cu-based filler wire and weld formation was greatly improved with the preheating of substrates when joining TC4 titanium alloy and 304 stainless steel. A Ti/Cu transition zone consisting of complex TiCu, Ti2Cu3, TiFe, and TiFe2 phases was formed between Cu-weld/TC4 interface, while Cu-weld/304ss interface was mainly composed of α-Fe and ε-Cu solid solution. At lower heat input, the undercut defect in back surface had potential to cause crack initiation and joint fracture. Though increasing heat input would improve weld morphology, the formation of thick interfacial reaction layer and weld cracking led to low weld quality and joint strength. The preheating of substrates had an obvious effect on wetting ability of liquid filler metal and could achieve a better weld quality at lower heat input. The back formation of weld was improved to decrease the occurrence of weld defects. The highest tensile strength of 365 MPa occurred at welding heat input of 0.483 kJ/cm, increasing by 47% compared to the joint without preheating. The interfacial reaction mechanism was discussed to reveal the relationship between microstructural characteristics and fracture behavior of Ti/steel welded joints with Cu-based filler wire.

Comparative Study on Laser Welding Thick-Walled TC4 Titanium Alloy with Flux-Cored Wire and Cable Wire

“…To address these problems, researchers have proposed improvements to the weld quality of titanium alloy by optimizing the welding process or supplementing it with new techniques, such as the use of different shielding gases [ 10 ], adjusting the heat input [ 11 ], numerical simulation-assisted optimization [ 12 ], applied magnetic fields [ 13 , 14 ], post treatment or pretreatment [ 15 , 16 , 17 ], and ultrasonic strengthening [ 18 ]. In addition to these ways to effectively improve the weld quality, the choice of wire type can also have a significant impact on the weld quality.…”

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].…”

Laser Cladding of Titanium Alloy Coating on Low Carbon Steel via Cu Interlayer

“…Although Cu-Ti IMC can be formed between Cu and Ti, the brittleness of Cu-Ti IMC [17][18][19] is lower than that of Fe-Ti IMC, which has a positive effect on mechanical properties of the joint. Furthermore, Cu has good plasticity, which can reduce the interfacial stress and thus improve the bonding performance of Ti/steel [20][21].…”