Microstructure and Mechanical properties of transition zone in laser additive manufacturing of TC4/AlSi12 bimetal structure

Ti/Al bimetallic structure (BS) has a good development prospect and broader application potential in aerospace engineering. Considering the limitation that dissimilar welding is only applicable to the thin plate, it is necessary to explore a new manufacturing process for Ti/Al BS. In this study, a TC4/AlSi12 BS was prepared by laser additive manufacturing (LAM). TC4 zone, AlSi12 zone and transition zone were formed in the LAM process. Due to the sufficient diffusion reaction, the transition zone with a width of about 0.8mm was obtained. At the same time, a few micro-cracks were found in the transition zone. The microstructure and phase composition of the transition zone had been emphatically studied. Research results showed that the presence of Si element made the phase composition of the transition zone more complicated. The structure evolution from TC4 to AlSi12 was: α-Ti → Ti3Al → TiAl+(TiAl+Si) → Ti5Si3 → TiAl3+(α-Al+Si) → α-Al+ Si +TiAl3 +(α-Al+Si) → α-Al+Si+(α-Al+Si). The hardness distribution of BS was uneven, with the highest value reaching 524HV. The tensile strength of the TC4/AlSi12 BS was about 110Mpa, and the fracture location was located in the transition zone.

Development and Evaluation of the Ultrasonic Welding Process for Copper-Aluminium Dissimilar Welding

The demand for joining dissimilar metals has exponentially increased due to the global concerns about climate change, especially for electric vehicles in the automotive industry. Ultrasonic welding (USW) surges as a very promising technique to join dissimilar metals, providing strength and electric conductivity, in addition to avoid metallurgical defects, such as the formation of intermetallic compounds, brittle phases and porosities. However, USW is a very sensitive process, which depends on many parameters. This work evaluates the impact of the process parameters on the quality of ultrasonic spot welds between copper and aluminium plates. The weld quality is assessed based on the tensile strength of the joints and metallographic examination of the weld cross-sections. Furthermore, the welding energy is examined for the different welding conditions. This is done to evaluate the influence of each parameter on the heat input resulting from friction at the weld interface and on the weld quality. From the obtained results, it was possible to optimise parameters to achieve satisfactory weld quality in 1.0 mm thick Al–Cu plate joints in terms of mechanical and metallurgical properties.

Effects of Rotation Speed on Microstructure and Mechanical Properties in Ti/Cu Dissimilar Friction Stir Welding

The dissimilar welding of titanium and copper by fusion welding is very difficult because the melting points of the materials are very highly different and strong brittle intermetallic compounds (IMCs) can be easily produced in welded zone and heat-affected zone, etc. Friction stir welding was employed as a type of solid-state welding for Ti/Cu dissimilar welding to obtain a sound welded zone and reduce the total process cost. This study investigated how the metal flow of the welded zone changes according to the variation in the rotational speed of the tool, from 450 rpm to 600 rpm. When the rotational speed was too high, the plastic flow of the softened material increased and intermetallic compounds such as TiCu, Ti2Cu3, and Ti2Cu, were generated in the Cu region of the welded zone. The microstructural evolution of AS (Advancing Side) and RS (Retreating Side) were investigated and the soundness of the welded zone and its mechanical properties were evaluated through the microstructural evolution. A high hardness value of 200 Hv or more was exhibited in some points, due to the formation of intermetallic compounds in the RS (Cu) region. Ti/Cu dissimilar friction stir welding at a welding speed of 50 mm/min and an appropriate rotation speed of 500 rpm showed a good welded zone and mechanical properties.

Experimental Investigation of Similar & Dissimilar Joints on Stainless Steel with TIG & MIG Welded

Now days, most of the structural fabrications possess welded joints that are produced using suitable welding technique. However, the joining of thick plates in a single pass welding is a cumbersome task to many fabricators. Likewise, the selection of welding technique, filler wire and welding condition for the similar and dissimilar welding of several metals is at the development stage. The similar and dissimilar metal joints of have been emerged as a structural material for various industrial applications which provides good combination of mechanical properties like strength, corrosion resistance with lower cost. Selections of joining process for such a material are difficult because of their physical and chemical properties. The stainless steel of similar and dissimilar material joints are very common structural applications joining of stainless steel is very critical because of carbon precipitation and loss of chromium leads to increase in porosity affects the quality of joint leads deteriorate strength. In the present study, stainless steel of grades 310 and 316 were welded by Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) welding with compound flux of 50 % SiO2 + 50 % TiO2 processes. The mechanical behavior like hardness, tensile strength and bending properties of similar and dissimilar metal joints were investigated. Keywords: Mechanical Properties, ATIG, MIG, SS310, SS316, Micro Structure.

Effect of Welding Groove and Electrode Variation to the Tensile Strength and Macrostructure on 304 Stainless Steel and AISI 1045 Dissimilar Welding Joint Using SMAW Process

AISI 1045 and 304 stainless steel are widely used in automotive and industrial fields However, both of these steels have their own advantages and disadvantages. AISI 1045 is not resistant to corrosion but has good wear resistance and low price. Meanwhile, the 304 stainless steel provides good corrosion resistance and mechanical properties but is costly. Their combination is able to provide a good property and reduce the costs. Thus, in order to combine these two metals, shield metal arc welding is carried out using welding groove and electrode variation. The groove variations used were double bevel, V, and double V-groove, additionally, the electrode variations used were E6013 and E7016. Then, the welding results were characterized using the tensile strength and macrostructure analysis. The results revealed that the specimen using E7016 electrode for the double V-groove resulted in the highest tensile test results the value of 270.48 MPa yield strength, 411.49 MPa tensile strength, and 19.81% elongation. The macrostructure analysis showed that the specimens using E7016 electrode gave a narrow HAZ that led to higher mechanical properties.

Dissimilar welding of high-entropy alloy to Inconel 718 superalloy for structural applications

High-entropy alloy, a new generation material, exhibits superior structural properties. For high-temperature applications, where dissimilar materials are in demand, HEAs may be joined with commercially available structural materials to improve their performance-life ratio. In this connection, a dissimilar joint was fabricated by gas tungsten arc welding between Al0.1CoCrFeNi-HEA and Inconel 718. The columnar dendritic grains are growing epitaxially at the Al0.1CoCrFeNi-HEA/weld metal interface, where their compositions are matching. While the composition misfit at the weld metal/Inconel 718 interface, reveals the non-epitaxial mode of solidification. In addition, the fusion zone exhibits the porosity and micro-segregation of NbC and Laves phases. The joint shows a joint efficiency of ~ 88%, where the strength is observed to be 644 MPa with 21% ductility. The results demonstrate the applicability of GTAW in fabricating the dissimilar weld joints between HEA and Inconel 718 for structural applications. Graphic abstract

Effects of interface conditions on heat and mass transfer during modeling of laser dissimilar welding

An improved 3 D heat and mass transfer model was developed to study the effects of interface conditions during modelling of laser dissimilar welding. In detail, the interface conditions consist of the physical processes at gas/liquid surface (e.g. free surface deformation and optical absorptance), substrate interface (e.g. mixture properties in liquid phase and thermal contact condition) and solid/liquid interface (e.g. fusion line). Their effects on heat and mass transfer are numerically and experimentally analyzed, which are all non-negligible in the welding modelling. In conclusion, free surface deformation influences convection flow and should be considered in the situation of micro-welding and high energy-input welding. Besides, the energy transfer between laser and substrate is more reasonably described by the optical absorptance expressed in polynomial function. The mass transfer induced variation of mixture properties is well described by the method based on time-dependent mixture fraction. Thermal resistance between clamp and substrate should be considered in the modelling of temperature field on macroscale. The joint conductance at substrate interface could be neglected when modelling heat and mass transfer inside the melt pool, while it should be calculated in the simulation of temperature distribution based on the mechanism of heat conduction. The obtained results in this paper provide a vital insight into the interface conditions in laser dissimilar welding process.

The Effect of Plume Generated on the Microstructural Behavior of the Weld Mixed Zone in High-Speed Laser Dissimilar Welding

Dissimilar laser welding has been researched to combine the excellent anticorrosion and high strength properties of Ti and the low weight and cost of Al. However, when welding dissimilar Al and Ti sheets, many kinds of intermetallic compound are easily generated. Therefore, intermetallic compounds and differences in material properties make joining such dissimilar metals very difficult. Previous studies clarified that ultra-high welding speed could suppress the weld defects. To elucidate the mechanism of Al and Ti dissimilar laser welding, material behavior of the weld fusion zone and components of fume generated during the ultra-high speed welding process were observed and analyzed using energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high speed cameras, and a spectrometer. The results show that the atom movement of Al and Ti in the weld plume affects the behavior of elemental components distributed in the weld fusion zone.