Tungsten Inert Gas Welding Brazing Research Articles

The study of microstructure and mechanical properties of Ti6Al4V/MB3 metallurgical joint by tungsten inert gas welding-brazing process

MB3 Mg alloy and Ti6Al4V alloy were joined by tungsten inert gas (TIG) welding-brazing process with AZ91 filler. The microstructures and mechanical properties of Ti-Mg weld were analyzed by optical metalloscope, scanning electron microscope and universal testing machine. Results reveal that Ti-Mg dissimilar alloys were successfully joined by TIG welding-brazing process. A Ti-Al intermetallic compound layer formed at the brazing area, and grain coarsening accompanied with Mg17Al12 precipitates occurred in the fusion area. The former is the key to realize the reliable joining of Ti-Mg, whereas the latter is the week point of whole joint. Besides, under optimized welding parameter of 65 A, the maximum mechanical property of 202 N mm−1 was obtained and fracture location was at the fusion area.

Improvement of Al/Steel Tungsten Inert Gas Welding–Brazing Joint by High-Energy Shot Peening

High-energy shot peening treatment was applied to improve the Al/steel tungsten inert gas welding–brazing lap joint. The mechanical properties and microstructure evolution of the joint were investigated. Results showed that the mechanical properties of weld were evidently reinforced due to microstructure transformation of joint surface layer. The grain structure in the joint surface layer was distorted and refined. Large compressive residual stress was introduced into the joint surface, and its hardness obviously increased due to strain hardening. When the peening pressure was 0.15 MPa, the tensile shear strength of the joint reached the maximum value (199.6 MPa), which was 16.5% higher than that of the as-welded joint.

Tungsten inert gas welding of dissimilar metals aluminum to titanium with aluminum based wire

The T40 and 5A06 alloy were welded by tungsten inert gas (TIG) welding-brazing technology. The effects of welding parameters on cross-section macrostructure, microstructure, mechanical properties and fracture features were investigated. During the TIG welding-brazing of Ti–Al, the low melting point Al alloy and filler metal melted and resulted in the formation of fusion welded joint, whereas the molten filler metal spread on the solid Ti plate and resulted in the brazed joint. TiAl3 IMC layer formed at the brazing area and the thickness of IMC increased with the increase of welding current. Besides, the thickness of IMC layer of lower zone is less than that of upper zone. The optimal performance of Ti–Al joint is gained under the current of 80 A and the highest joining strength reaches 235 MPa. However, as the current exceeded 80 A, tensile strength of joint decreased owing to the metallurgical defects at the fusion welding area and brazing area.

Microstructure and mechanical properties of tungsten inert gas welded–brazed Al/Ti joints

The tungsten inert gas welding–brazing process using Al-based filler metal has been developed for joining 5052 Al alloy to Ti–6Al–4V alloy in a butt configuration. The results indicated that heat input influenced the morphology and thickness of the interfacial reaction layer of Al/Ti joints, which played an important role in the mechanical properties of weldment. With the optimised tungsten electrode offset D of 1.0 mm from Al/Ti initial interface to Al side and welding current of 70 A, the thin cellular-shaped and club-shaped TiAl3 reaction layers formed in the brazing zone, which contributed to suppressing crack initiation and propagation during tensile test. Eventually, the maximum tensile strength of 183 MPa was obtained and the optimised Al/Ti joint fractured at Al alloy base plate. Moreover, the power density characterisation and joining mechanism of Al/Ti joints were discussed.

Tungsten Inert Gas Welding–Brazing of AZ31B Magnesium Alloy to TC4 Titanium Alloy

Tungsten inert gas (TIG) welding–brazing technology using Mg-based filler was developed to join AZ31B Mg alloy to TC4 Ti alloy in a lap configuration. The results indicate that robust joints can be obtained with welding current in the range of 60–70 A. The joint interface was found to be likely composed of Mg–Ti diffusion reaction layer accompanied with Mg17Al12 precipitate phase, indicating that metallurgical joining was achieved. The optimized joint with average tensile-shear strength of 190 N/mm2 was obtained and fracture occurred at the Ti/fusion zone interfacial layer during tensile test. Moreover, the fracture surface was characterized by equiaxed dimple patterns accompanied with a few lamellar tearing. Finally, finite element modeling (FEM) numerical simulation was developed to analyze the distribution characteristics of the temperature field of joints.

Reinforcement of Mg/Ti joints using ultrasonic assisted tungsten inert gas welding–brazing technology

Ultrasonic assisted tungsten inert gas welding–brazing technology was developed to refine coarsening columnar α-Mg grains of Mg/Ti joints. In this study, ultrasonic vibration was introduced into molten pool of Mg/Ti joints with frequency of 20 kHz and maximum power of 1·6 kW. The results showed that, with ultrasonic power of 1·2 kW, the morphology of columnar α-Mg grains was refined to approximately equiaxed grains and the average grain size of columnar grains decreased from 200 to ∼50 μm. Moreover, the maximum joint strength of joints increased ∼18·1% to 228 N mm−1 over the joints welded without ultrasonic vibration (193 N mm−1). Furthermore, the optimised Mg/Ti joint fractured at base metal zone rather than fusion zone upon tensile–shear loading, indicating that efficient grain refinement was attained. However, welding voids occurred with the ultrasonic power further increased to 1·6 kW, which resulted in the decrease in mechanical properties.

Analysis of intermetallic layer in dissimilar TIG welding–brazing butt joint of aluminium alloy to stainless steel

Intermetallic layer of dissimilar tungsten inert gas welding–brazing butt joint of aluminium alloy/ stainless steel has been studied. A visible unequal thickness intermetallic layer has formed in welded seam/steel interface, and the thickness of the whole layer is <10 μm. The interface with Al–12Si filler metal consists of τ5-Al8Fe2Si layer in welded seam side and θ-(Al,Si)13Fe4 layer in steel side with the hardness values of 1025 and 835 HV respectively, while the interface with Al–6Cu filler metal consists of θ-Al13(Fe,Cu)4 layer with the hardness of 645 HV. The average tensile strength of the joint with Al–12Si filler metal is 100–120 MPa, and the fracture occurs at θ-(Al,Si)13Fe4 layer, while the joint with Al–6%Cu filler metal presents high crack resistance with tensile strength of 155–175 MPa, which reaches more than 50% of aluminium base metal strength.

Metallurgical and mechanical investigations of aluminium-steel butt joint made by tungsten inert gas welding–brazing

Dissimilar metals of 5A06 aluminium alloy and SUS321 stainless steel were butt joined by tungsten inert gas welding–brazing with BJ380A filler metal and modified non-corrosive flux. The interface in seam/steel is made up of two kinds of intermetallic phase layers, τ5-Al7Fe2Si phase in the seam side and θ-FeAl3 phase in the steel side. The granular phase in welded seam is CuAl2, and the lath shaped phase is τ6-Al5FeSi. In the fusion area, the chainlike phase is Al–Si eutectic structure, and the block-like phase is Al6(Fe,Mn). The tensile strength of the butt joint reaches 125 MPa, and fracture occurs at τ5-layer, with highest hardness value of 950 HV. The present joint without coated layer can reach the same level to those with coated layer.