As a highly effective welding method, PPCA-TIG (Powder Pool Coupled Activating Flux–Tungsten Inert Gas) welding aims to achieve automated activation of TIG welding through the use of suitable ...activating fluxes. However, due to the unique transitional behavior of activating elements, the mechanism of PPCA-TIG is a little bit different from common activating TIG welding. In this research, a two-dimensional model is established to investigate the effect of four activating fluxes (TiO2, SiO2, MnO2, CaF2) on arc morphology and force. A series of welding experiments is performed to study the impact of the different activating elements on the molten pool. The results show that the increase in the penetration of TiO2 is related to the high arc temperature and great arc force and electromagnetic force in the molten pool. The problem of the softening of 3003 aluminum alloy welded joints is solved. Other activating fluxes are less effective than TiO2. The addition of calcium fluoride significantly affects penetration. The use of TiO2, SiO2 and MnO2 changes the molten pool viscosity and affects the molten pool oscillation, thus affecting the weld quality.
The tungsten inert gas (TIG) welding-brazing technology using Mg based filler was developed to join AZ31B Mg alloy to TA2 pure Ti in a lap configuration. The results indicate that robust joints can ...be obtained with welding current in the range of 60-70 A and welding speed of 0·2 m min
−1
. The joints were found to be composed of the coarse grained fusion zone accompanied with the precipitated phase of Mg
17
Al
12
, and a distributed Mg-Ti solid solution zone at the interface of Mg/Ti, indicating that metallurgical bonding was achieved. The maximum tensile-shear strength of 193·5 N mm
−1
, representing 82·3% joint efficiency relative to the Mg alloy base metal, was attained. The optimised Mg/Ti joint fractured at Mg fusion zone upon tensile-shear loading, mainly caused by grain coarsening. Moreover, the fracture surface practically consisted of scraggly areas, which was characterised by equiaxed dimple patterns accompanied with a few lamellar tearing.
The frequently used aerospace materials, i.e., ultra-high-strength maraging steel (250) and corrosion-resistant 13-8 Mo stainless steel in the solution-annealed and cold-worked condition, have been ...joined by three fusion welding processes, namely interpulse TIG welding, and high energy density fusion processes like electron beam welding (EBW) and laser beam welding (LBW). The interpulse TIG welding process was carried out by using W2 grade maraging steel filler wire. The dissimilar joints were welded by EBW and LBW processes without any filler wire. All the dissimilar welded joints were characterized by microstructural observations and validated by mechanical properties in the as-welded as well as precipitation-hardened conditions after welding. The weld microstructures and microhardness profiles were correlated to the tensile strength of weld. Electron beam welded joint with precipitation hardening after welding, i.e., soaking at 510 °C and subsequent air cooling, demonstrated the superior mechanical properties among all the welds.
The effect of welding and subsequent annealing on the evolution of the crystallographic texture and the anisotropic properties in a 2205 duplex stainless steel was studied. A strong texture was found ...in the base metal for both austenite and ferrite phases. The austenite texture is composed of rolling (copper and brass) and recrystallization (cube) components whereas the ferrite texture contains mainly a marked <
001>//RD α fibre with a major rotated cube component. The texture evolution during welding and annealing was characterized in the base metal, heat affected zone and weld metal; the corresponding phase proportions and misorientation values were also calculated. The analysis of all these data allows improving the understanding of the recovery, recrystallization and grain growth mechanisms occurring during the various steps of the treatment. Finally, a micromechanical model was used to calculate some mechanical properties from the measured texture, and to confirm that the optimal annealing treatment is about 1050
°C.
► The crystallographic texture in annealed DSS weld joint has been studied. ► Both deformation and recrystallization textures were found in the base material. ► The misorientation distribution in the weld metal is typical from phase transformation. ► Annealing at 1050° for 1
h give a better homogeneity of the mechanical properties.
The angular distortion is a typical out-of-plane distortion, and it has negative effects on the performance of welded structures. However, the researches on angular distortion of welded structures ...using intelligent algorithm and mathematical analysis are comparatively less. In this article, the influence from the bead profile on the angular distortion is analyzed, and the angular distortion of tungsten inert gas arc welding with no gap would be predicted by back propagation neural network and the novel inherent strain considering the actual bead geometry model, and the prediction accuracy is also evaluated through comparative analysis of the results with each other. The average relative error of the model built using inherent strain considering the actual bead geometry model method is only 1.289 % and better than that predicted by back propagation neural network algorithm (4.772 %). Meanwhile, the inherent strain considering the actual bead geometry model prediction stability that is estimated using standard deviation is also clearly better than that of back propagation neural network. Actually, the prediction methods by back propagation neural network algorithm and inherent strain considering the actual bead geometry model are proved to be correct and stable. Therefore, the proposed methods can be used to predict the angular distortion of the welded structures with no gap butt joint and guide the actual welding process to decrease the welding deformation.
An important part in affecting the properties of the titanium alloy VT22 is a heat treatment (HT). Annealing of welded joints of the alloy also works as strengthening HT. Depending on the heating ...temperature, duration of annealing and the cooling rate, different combinations of strength and ductility could be obtained. Annealing is carried out in the VT22 alloy two-phase region (750 - 850 °C) followed by direct or stepwise cooling. This heat treatment results in a maximum heterogeneity of the structure with nearly an equal amount of α and β phases. It also provides a tensile strength of 1100 - 1300 MPa.
Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and ...development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation.
Aluminium 7075 being the workhorse of the Aluminum series has a wide range of applications in industries like aerospace, automotive, transport, etc. due to its high strength to density ratio, light ...weight and good corrosion resistance. It has been observed that it is difficult to weld the 7075 alloy using Tungsten inert gas (TIG) welding metal inert gas (MIG) welding or any other conventional method as it encounters solidification and recrystallization problems like cracking and porosity which hamper the weld strength. Hence, in this paper we have attempted to weld the 7075 alloy using friction stir welding, a solid state welding process that does not involve the melting of the sample and hence avoids problems related to solidification of the weld. The weld strength of the same is tested by applying tensile test, hardness test and microstructure analysis. The aforementioned tests are applied on the 7075 alloy welded by autogenous TIG welding and the weld strength of the two welding methods is compared
Present study is planned to analyze the effects of welding process parameters on quality characteristics of TIG welded 316L austenitic stainless steels (ASS). The input parameters considered in the ...study are: welding current, speed and gas flow rate. Butt-joints of ASS sheets have been made as per Box-Behnken design of response surface methodology (RSM). After welding operation, tensile tests have been conducted on welded samples and observations of ultimate tensile strength (UTS) has been noted. Mathematical modeling has been made to relate the input parameters and output response by RSM. Teaching leaning-based optimization (TLBO) approach has been used to optimize the UTS. The influences of input welding parameters on UTS has been studied and analyzed through contour plots. Confirmatory tests have been conducted to validate the predicted parametric condition obtained by integrated RSM and TLBO. From the study, it is found that RSM and TLBO is efficient to maximize UTS in TIG welding operation.
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