TIG-welded Joints Research Articles

The microstructure and mechanical properties of the friction stir processed TIG-welded aerospace dissimilar aluminium alloys

The AA6082-T651 and AA8011-H14 dissimilar aluminium alloys were utilised in this study. The dissimilar aluminium alloys were joined using tungsten inert gas (TIG) welding technique. TIG welding is the most used welding technique for aerospace engineering applications. However, the joining of dissimilar alloys comes with its drawbacks. The friction stir processing technique comes as a microstructural modifying technique to improve the associated joint defects. The TIG-welded AA6082/AA8011 dissimilar aluminium joints were studied comparatively with the friction stir processed TIG-welded AA6082/AA8011 joints. This was done to investigate the impact of the friction stir processing on the microstructure and mechanical properties of the said TIG-welded joints. The results showed that the application of FSP on the TIG-welded joints resulted in a decrease of minimum grain size of 12.41 to 3.68 µm. The ultimate tensile strength increased from 86.9 to 90.2 MPa. The stir zone hardness also increased from 55 to 68 HV.

Experimental investigation of bending and tensile strength of friction stir processed TIG-welded AA5083-H111 joint

This paper reports on the experimental investigation of bending and tensile strength of the friction stir processed TIG-welded AA5083-H111 joint. The friction stir processed joint was studied comparatively with the TIG-welded joint (unprocessed joint). The TIG-welded joint was processed using a single-pass friction stir processing technique. The microstructural analysis revealed that the unprocessed joint was dominated with coarse grains while the refined grains dominated the friction stir processed joint. The unprocessed joint consistently failed at the center of the joint during tensile testing while the processed joint failed in different locations of the stir zone. The tensile strength of the unprocessed joint was found to be 47.4% to that of the base metal while that of the processed joint was found to be 76.5% to that of the base metal. The percentage elongation of the processed joint was found to be 82.4% to that of the base metal while that of the unprocessed joint was found to be 34.8% to that of the base metal. The bending failure mode of the processed and unprocessed joint was similar to that observed during tensile testing.

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy TIG-welded joint

Abstract Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas (TIG) welded joint were analyzed in detail. In weld zone (WZ), α+θ eutectic structure formed at grain boundaries with no precipitates inside the grains. In partially melted zone (PMZ), symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-like θ′ phases appeared in the secondary heated zone. In over aged zone (OAZ), the coarsening and dissolution of θ′ phases occurred and most θ′ phases transformed into θ phases. In general heat affected zone (HAZ), θ′ phases coarsened. Factors such as the strengthening phases, the grain size, the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint. Moreover, a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates, the average diameter of precipitates and the concentration of soluble elements was proposed.

Corrosion Behavior Evaluation of TIG Welding Joint of Low Carbon Steel

The current research studies the corrosion behavior of Low Carbon Steel 1020 AISI welded joint by means of TIG welding method using mutable DC current and constant voltage. Before the welding process, shot peening by steel balls for certain welded joints is applied to the sheet metal, and then welding under the same welding conditions without shot peening. A number of corrosion inspection samples have been prepared with the measurements of (15 * 15 * 3 mm), according to ASTM (G71-31). Microstructure, residual stress has been tested and the corrosion test has been conducted electrochemically in 3.5 per cent NaCl solution for all samples. Corrosion rate was computed by means of the Tafel equation. The results show a rise in corrosion rate in some welded joints compared with other welded joints and base metal due to the variation in heat input from the input current for each weld passes. Shot peening process contributed to lower corrosion rate compared to welded joints without shot peening, due to the residual compression stresses produced by shot peening process. The best results obtained when number of welds passes and welding current are decreased to get suitable heat input.

Microstructure, mechanical properties and pitting corrosion of TIG weld joints alternative low-cost austenitic stainless steel grade 216

This present work aims to study 200 series austenitic stainless steel as a replacement for 300 series austenitic stainless steel. This is due to 200 series austenitic stainless steel being inexpensive and also due to its popularity in Southeast Asia. This study investigated the behavior and properties of the weld metal produced from 216 grade austenitic stainless steel. The microstructure, mechanical properties and pitting corrosion resistance that were produced by the tungsten inert gas welding process (TIG) with filler metal ER316 are studied in this paper. The variable parameters of the welding process were heat inputs at high (0.78 kJ/mm), medium (0.52 kJ/mm) and low (0.39 kJ/mm) ranges. It was found that the weld metal with a high heat input level increased the width of the face weld, root weld, PMZ and HAZ. However, the opposite result was achieved when the heat input was reduced. The microstructure of all the weld metals formed delta-ferrite content in the austenite matrix. This was shown to be greater in the weld metal with a low heat input, under the solidification mode FA. The results were shown to agree with the predictions outlined in the Schaeffler diagram. In addition, it was discovered that a high heat input level produced a more discontinuous form of delta-ferrite content than for the low heat input model. This corresponded to the dendrite length and inter-dendrite spacing in the weld zone. The hardness, ultimate strength and elongation tended to decrease when the heat input increased. The fractures for all the weld metals were found to occur in the location of the weld zone. The pitting corrosion resistance increased when the heat input was reduced, which related to the volume of delta-ferrite content in the weld metal zone. This corresponds to the pitting corrosion resistance in the weld metals being higher than for the base metal material. Furthermore, it was found that pitting occurred initially at the interface between the delta-ferrite and austenite phase and the corrosion then spread into the austenite phase.

Friction stir welding of ultra high-purity aluminium thin sheets never to lower high conductivity at ultra-low temperature

ABSTRACT Ultrahigh-purity aluminium sheets with excellent electrical and thermal conductivity at ultra-low temperature have uses in heat dissipation components in, for example, superconducting equipment. Recently, here has been a requirement for the development of methods of welding these sheets without degrading their excellent conductivity. This study focused on friction stir welding (FSW), which was conducted for 99.999 wt.% (5 N) Al thin sheets with thickness of 0.8 mm. The FSW tool rotation speed was set to 3000 rpm, and both the welding speed and tool insertion depth were varied. Decreasing welding speed suppressed the occurrence of a kissing bond on an FSW back side and increased the area of the stir zone that had ultrafine grains, although residual strain in all the joints was greater than in tungsten inert gas (TIG)-welded joints which consisted of coarse grains similar to the base metal. Fracture occurred in the base metal in tensile tests of the FSW joints except for those made at the maximum welding speed, in contrast to rupture near the fusion line of the TIG-welded joint due to blowholes. On the other hand, the residual resistivity ratio (RRR) of FSW and TIG-welded joints decreased to almost half of that of the base metal. The heat treatment at 500°C for 3 h increased the RRR of the FSW joints to almost the same value as that of the base metal. This is attributed to a significant reduction of residual strain as well as grain coarsening. In TIG-welded joint, there is an evident decrease in the RRR associated with a decrease in purity. Therefore, FSW in conjunction with post-weld heat treatment would be a better choice to achieve high conductivity at ultra-low temperatures in 5 N-Al thin sheet joints, while maintaining a high joining strength.

Influence of Friction Stir Processing on Weld Temperature Distribution and Mechanical Properties of TIG-Welded Joint of AA6061 and AA7075

The joining of dissimilar materials is required in many engineering and defense applications, and the conventional fusion welding often results in defective welds. The friction stir welding has minimized the welding defects, but not completed. This work focuses on the effect of friction stir processing on TIG-welded joints with filler ER 5356 to improve the mechanical properties of TIG-welded joints. In this paper, the FSP tool pin rotates on an already welded joint by TIG welding to lower the welding load and improve the weld quality by adjusting the processing parameters of friction stir processing. After analyzing the mechanical properties of TIG + FSP-welded joint, computational fluid dynamics-based numerical model was developed to predict the temperature distribution and material flow during TIG + FSP of dissimilar aluminum alloys AA6061 and AA7075 by ANSYS fluent software. The minimum compressive residual stress 18 MPa, maximum tensile strength (281.1 MPa) and hardness (107 HV) were located at the nugget zone of the TIG + FSP weldment at tool rotation speed of 1300 rpm, traverse speed of 30 mm/min and tilt angle 2°. The predicted peak values of temperature at the weld region were calculated and the maximum temperature (505 °C) and maximum heat flux (2.93 × 106 w/m2) were observed at a tool rotation of 1300 rpm.

Mechanical Properties of Dissimilar TIG-Welded ARAA and SS316L Joint

An advanced reduced activation alloy (ARAA) has been developed as a structural material for breeding blankets in fusion reactors. A breeding blanket has a relatively complex structure, so various welding methods, such as electron beam welding and similar and dissimilar tungsten inert gas (TIG) welding have been developed for the manufacture of breeding blankets. In this article, mechanical properties of joints of dissimilar TIG welding are introduced using ARAA and SS316L. Charpy impact, tensile, and bending tests were carried out for the as-postweld heat-treated (PWHT) samples manufactured with defined welding conditions, and hardness tests were conducted for the as-welded and the PWHT samples. The average hardness values of the dissimilar welded samples were 338 HV in the heat-affected zone (HAZ) and 199 HV in the weld metal (WM). The PWHT decreased hardness to 223 HV in the HAZ but did not affect the hardness in the WM. The yield strength (YS) and ultimate tensile strength (UTS) of the dissimilar TIG welds were 335 and 617 MPa, respectively.

Microstructure and Mechanical Properties of TIG and Friction Stir Welded Joints of Sc-contained High Strength Aluminum Alloy Sheet

Microstructure and Mechanical Properties of TIG and Friction Stir Welded Joints of Sc-contained High Strength Aluminum Alloy Sheet

Dissimilar metal welding of P91 steel-AISI 316L SS with Incoloy 800 and Inconel 600 interlayers by using activated TIG welding process and its effect on the microstructure and mechanical properties

This study investigates dissimilar metal weldments between P91 steel and AISI 316 L austenitic stainless steel fabricated by activated TIG welding (A-TIG) with and without the use of interlayers of Incoloy 800 and Inconel 600. Through thickness penetration in 8 mm thick plates was achieved in a single pass A-TIG welding using a pre-coated mixture of metallic oxides. Hot cracking was eliminated in A-TIG weld joints in contrast to conventional TIG weld joints without flux. Fully martensitic structure was observed in the weld metal developed without the use of interlayer. Microstructural modifications were achieved with the use of interlayers. The weldment with Incoloy 800 interlayer exhibited martensitic-austenitic structure whereas fully austenitic structure was observed with Inconel 600 interlayer. Interlayers improved impact toughness and ductility of the weld joints without significant loss of tensile strength. The effect of interlayers on carbon migration after aging treatment (620 °C/500 h) was evaluated with the help of thermodynamic simulations and it was observed that the use of interlayers reduced the severity of carbon migration.

Effects of weld penetration on tensile properties of 2219 aluminum alloy TIG-welded joints

Abstract Numerical simulation and experimental methods were used to investigate the effects of weld penetration on tensile properties of 2219 aluminum alloy tungsten inert gas (TIG) welded joints. The results show that when other geometric parameters are consistent, within a certain range, the deeper the weld penetration of the capping weld is, the lower the tensile strength of the joint is. The deeper weld penetration of the capping weld can cause the more concentrated stress at the weld toe and the joint is more likely to crack accordingly. Based on necessary assumptions, a model for analyzing the mathematical relation between the weld penetration of the capping weld and the tensile strength of the joint was proposed to validate the experimental results. The decrease of weld penetration of capping weld can be controlled by decreasing welding current, helium content or increasing welding voltage.

Mixing Design for ATIG Morphology and Microstructure Study of 316L Stainless Steel

This work is a study of the effects of oxides combination on the morphology of 316L stainless steel welds. A series of thirteen weld lines were carried out using thirteen different oxides. Based on the depth and ratio D/W results, three candidate oxides were selected: Ti2O, Mn2O3, and SiO2. Mixing method available in Minitab 17 software is the most appropriate method to find the optimal combinations to get the best depth and D/W ratio. According to simplex lattice degree four, nineteen combinations of these oxides were prepared. The results show that the optimal composition of flux was: 66%SiO2-34% Mn2O3. The depth and D/W ratio increased to 8.85mm and 0.98 respectively for optimal ATIG, whereas for the conventional TIG welding, the depth and the ratio D/W didn't exceed 1.65mm and 0.17 respectively. For TIG weld joint the hardness is about 47 HRA and it increases to 77 HRA for the optimal ATIG weld joint. The absorbed energies in Charpy impact test are 146 and 138kJ in the weld zone and in the heat affected zone respectively for the TIG welding and they dropped to 111 and 74kJ for the optimal ATIG welding. The fracture surface examined by scanning electron microscope (SEM) shows a ductile fracture for TIG weld with small dimples but ductile-brittle fracture for ATIG weld. Energy dispersive spectroscopy (EDS/SEM) analysis shows the formation of FeS2 and SiO2 in the weld zone causing low absorbed energy for ATIG weld.

Effects of Post-weld Heat Treatment on Microstructure, Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows different microstructure and microhardness due to the different welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing effect on the weld and their existence was more of an adverse effect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.

Study on the inconsistency in mechanical properties of 2219 aluminium alloy TIG-welded joints

The strength and plasticity of 2219 aluminium alloy tungsten inert gas (TIG)-welded joints are inconsistent, which can compromise the safety of products. Both numerical simulation and experimental methods are used to study why the mechanical properties show a significant variation among 2219 aluminium alloy TIG-welded joints; the reasons can be summarized as involving geometric factors and metallurgical factors. Changes in the front weld width, the penetration depth of the capping weld, and other geometric parameters can have different effects on joints' mechanical properties. Three types of metallurgical factors can negatively affect joints' mechanical properties: i) unfavourable eutectic structure (the presence of coarsened eutectic particles and a thickened grain boundary eutectic structure in the crack initiation region of C10S+C10S welded joints; and the appearance of a continuously elongated eutectic structure close to the fusion line near the crack initiation region of C10S+CYS-welded joints); ii) significant segregation in the weld zone (WZ); and iii) decreased microhardness values in the partially melted zone (PMZ) and in the WZ. Two methods can be adopted to improve the joints' mechanical properties: i) The shapes of the welded joints can be optimized by adjusting the welding process parameters. One example is decreasing the penetration depth of the capping weld by decreasing the welding current and gas flow rate during the second pass. ii) The degree of segregation in the WZ and PMZ can be reduced by properly adjusting the welding heat input and wire feeding speed.

Process Parameter Optimization in TIG Welding of AISI 4340 Low Alloy Steel Welds by Genetic Algorithm

Weld quality is an essential requirement to the fabrication and construction industries. In this present investigation, an attempt has been made to optimize the process parameters of Tungsten Inert Gas (TIG) welding of AISI 4340 low alloy steel. Taguchi L9 orthogonal array is used to design the experiment and response surface methodology was used to develop mathematical model and the process parameters were optimized using Genetic Algorithm (GA). The important process parameters namely welding current, voltage, welding speed, and gas flow rate are considered. The results indicate that the current and voltage have a maximum influence on improving Ultimate Tensile Strength (UTS) in TIG-welded joint.

Thermo-Mechanical Analysis of Activated Tungsten Inert Gas Welding (A-TIG) of Type 316LN Stainless Steel Thin Plates

Abstract In the present study, thermo-mechanical behavior of 316LN stainless steel thin plates during activated tungsten inert gas (A-TIG) welding was investigated using SYSWELD®. A-TIG welding was carried out with more reduced heat input for fabricating 3-mm-thick 316LN stainless steel plates than that of the conventional TIG welding process. Induced transient temperature during welding was measured using a K-type thermocouple. A pulse-echo ultrasonic test was carried out using a 2-MHz probe employing critically refracted longitudinal waves for measuring residual stresses across the weld joint. A digital height gauge was used to quantify the distortion caused during welding. There was a good agreement between the predicted and measured thermal cycles, residual stresses, and distortion. The concentrated heat intensity of A-TIG welding induced higher surface temperature in the weld center, produced a narrow weld bead, and exhibited a sharp temperature gradient at the weld/base metal interface. Peak residual stress and distortion of the A-TIG weld joint were found to be less than that of the TIG weld joint.

ANALISIS SIFAT MEKANIK LAS TIG PADA PLAT ALUMINIUM SERI 5 DENGAN VARIABEL KUAT ARUS 65; 70; 75 A UNTUK MANUFAKTUR KENDARAAN AIR SAMPAN (CANOE)

Abstract: In general, water vehicles or water transport commonly called canoes are still used in villages for fishermen to fish in the sea and in rivers. Aluminum alloy in this research using Aluminum series 5. Background of this research is to analyze the strength of TIG weld (Tungsten Inert Gas) connection in the canoe to get reliable samples and no leakage. In high TIG welding the low temperature is determined by the high-low of the electric current being flowed. The aluminum plate for the canoe is subjected to material composition testing and tensile testing to determine the physical and mechanical properties of the TIG welding joints on the aluminum series 5. TIG welding with the current variable 65, 70 and 75 Ampere. Testing specimens of 2mm thick with dimensions of 24x16 cm where the electric arc flame is generated by tungsten electrodes (non-feeding electrodes) with metal workpieces. Test results obtained include that welding on aluminum series 5 is done with AC current (Alternating Current) due to the action of cleaning the metal surface is greater. Thin metal work, TIG welding can be used without metal filler. Material composition test showed that aluminum content of 97,76% and magnesium main addition element equal to 1.753%. In tensile testing, the strong variations of current used to connect aluminum plates are 65, 70, and 75 Ampere produce different tensile strength. The highest tensile strength is generated on plate grafting using a strong current of 75 Ampere with a yield of 165.91 MPa. This is because with a strong current of 75 A, the welding liquid enters and fuses into the center of the aluminum, resulting in a strong welding joint.

Residual Stress Measurements on the TIG Weld Joint of 57Fe15Cr25Ni Austenitic Steel for Structural Material Applications by Means X-Ray Diffraction Techniques

Residual Stress Measurements on the TIG Weld Joint of 57Fe15Cr25Ni Austenitic Steel for Structural Material Applications by Means X-Ray Diffraction Techniques

Microstructure analysis and mechanical characteristics of tungsten inert gas and metal inert gas welded AA6082-T6 tubular joint: A comparative study

The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding (TIG) and metal inert gas welding (MIG) processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-welded specimens. The extent of the heat-affected-zone (HAZ) in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.

Effects of Post-welding Heat Treatment of TIG Welding Joint of Al-Zn-Mg Alloy

Effects of Post-welding Heat Treatment of TIG Welding Joint of Al-Zn-Mg Alloy