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Showing papers on "Heat-affected zone published in 2020"


Journal ArticleDOI
TL;DR: In this paper, the microstructure and mechanical behavior of the dissimilar welded joint (DWJ) between ferritic-martensitic steel and austenitic grade steel along with its application have been summarized in Ultra Super Critical (USC) power plant.

126 citations


Journal ArticleDOI
TL;DR: In this article, the microstructural and mechanical evolution of friction stir welded 6061-T6 aluminum alloy, the influence of notch locations on impact and fatigue crack growth (FCG) behavior were evaluated.

52 citations


Journal ArticleDOI
TL;DR: In this article, a detailed investigation of the effect of cladding parameters on the crack susceptibility was carried out on coupons that received a low pre-heating condition, and attempts were made to reduce crack defects by using an induction preheating, with higher temperatures in the range of 800-1100°C.

42 citations


Journal ArticleDOI
TL;DR: In this article, the microstructure and mechanical properties of dissimilar metal weld joints between AISI 316L SS-Alloy 800 developed by activated TIG (A-TIG) welding are discussed.
Abstract: The present work discusses the microstructure and mechanical properties of dissimilar metal weld joint between AISI 316L SS-Alloy 800 developed by activated TIG (A-TIG) welding. The evolution of fusion zone microstructure and solidification temperature range were investigated through equilibrium calculation and Scheil-Gulliver equation. Electron probe micro-analysis revealed the micro-segregation of Ti and Si in the inter-dendritic arms of the fusion zone. The presence of secondary phases (Ti(C,N) and FeSi2) in the fusion zone was confirmed with X-ray diffraction technique and transmission electron microscopy of electrochemically extracted precipitates. The A-TIG weld joint showed a decent combination of tensile strength and impact toughness. Tensile testing with digital image correlation revealed a transfer of strain localization from Alloy 800 side heat affected zone to the fusion zone due to lower hardening capacity of the fusion zone. During tensile loading, the formation of micro-cracks along the solidification grain boundaries reduces the peak tensile strength of the fusion zone.

42 citations


Journal ArticleDOI
TL;DR: In this article, the parameters of fatigue crack growth rate for Q355J2 steel exposed to air and seawater were presented using the Paris' law based on the stress intensity factor (SIF), J-integral, crack tip opening displacement (CTOD), and crack tip tip opening angle (CTOA).

42 citations


Journal ArticleDOI
TL;DR: In this paper, the relationship between the microstructures and mechanical properties was built for the double-side FSW butt joint with more attention paid to the local characteristic zones, where a phenomenon of microstructural inhomogeneity existed in the nugget zone (NZ) through the thickness direction.

39 citations


Journal ArticleDOI
TL;DR: In this article, the forming mechanism of fusion zone polygonal porosity and heat affected zone (HAZ) liquation cracking were systemically investigated and possible solutions to the welding process were also proposed.
Abstract: In this study, we present experimental laser welding SUS304 stainless steel to T2 copper. The forming mechanism of fusion zone polygonal porosity and heat affected zone (HAZ) liquation cracking were systemically investigated and possible solutions to the welding process were also proposed. We deemed that the generation of HAZ liquation cracking mainly underwent three stages: crack incubation, crack initiation and crack growth. Formation of HAZ liquation cracking was closely related to precipitation of Cu-Fe compounds at grain boundaries and grain boundary liquation. The occurrence of porosity was determined by the keyhole instability correlated with fluid flow, keyhole free surface evolutions and composition segregation in a welding process. The susceptibility to HAZ liquation cracking can be effectively lowered by controlling the heat input during laser welding. In addition, the porosity in the fusion zone can be eliminated by reasonably adjusting laser deflection angle in the experiments, which greatly improved the microstructure and mechanical properties of welded joints.

36 citations


Journal ArticleDOI
TL;DR: In this article, the effects on the weld-bead geometry and heat affected zone from high and low frequency pulsed current are explored on Gas Tungsten Arc Welding (GTAW).

36 citations


Journal ArticleDOI
Yue Mao1, Yu Ni1, Xuan Xiao1, Dingqiang Qin1, Li Fu1 
TL;DR: In this article, dissimilar butt joints of 1.0 mm thick 6061-T6 aluminum alloy and T2 pure copper ultra-thin sheets were fabricated using micro friction stir welding under various tool traverse speeds while the rotational speed was 3000 rpm.

33 citations


Journal ArticleDOI
TL;DR: In this paper, high-strength low-alloy (HSLA) steels with a yield strength of 800 MPa and a thickness of 8 mm were subjected to laser welding to address the problem of loss of strength in the welded joint.

33 citations


Journal ArticleDOI
TL;DR: In this paper, the mechanical properties of ultra-high strength steels (UHSSs) with nominal yield stress of 960 and 1100 MPa after welding were investigated. And the results showed that the S960, a direct-quenched type of steel, showed a considerable reduction in its hardness and tensile strength up to 29 and 32%, respectively.
Abstract: This paper presents an investigation into the mechanical properties of ultra-high strength steels (UHSSs) (with nominal yield stress of 960 and 1100 MPa) after welding. Seven weld thermal cycles were simulated using a Gleeble 3800 thermal-mechanical machine. These cycles represented the temperature-time history of the joint at various distances from the weld fusion line (FL) in a typical gas metal arc welding (GMAW) process. The mechanical properties such as Vickers surface hardness, uniaxial tensile behavior and Charpy impact toughness were examined. Microstructural evaluation using field emission scanning electron microscopy (FESEM) was also conducted. According to the results, the S960 which was a direct-quenched type of steel, showed a considerable reduction in its hardness and tensile strength up to 29 and 32%, respectively. On the other hand, the S1100 which was manufactured via quenched and tempered process, showed only a minor degree of softening at far distances from the weld FL (up to 4%) followed by 2% tensile strength reduction, and hardening close to the FL (up to 13%). Microstructure analysis has been carried out to provide insight to the change of mechanical properties in UHSS after welding.

Journal ArticleDOI
TL;DR: Conventional P91 and boron modified P91-steels were considered in the present investigation using Gleeble, weld intercritical heat-affected zone (ICHAZ) was processed Conventional microscopy was used as discussed by the authors.
Abstract: Conventional P91 and boron modified P91-steels were considered in the present investigation Using Gleeble, weld intercritical heat-affected zone (ICHAZ) was processed Conventional microscopy was

Journal ArticleDOI
TL;DR: In this article, the individual effect of rotational speed, feeding rate and plunge depth on the weld strength of an AA6082-T6 aluminum alloy produced by Refill Friction Stir Spot Welding was investigated.
Abstract: Process parameters optimization was carried out to evaluate the individual effect of rotational speed, feeding rate and plunge depth on the weld strength of an AA6082-T6 aluminum alloy produced by Refill Friction Stir Spot Welding. Statistical analysis allowed to maximize the weld peel and shear strength and a strong correlation between plunge depth and weld resistance was found. It was shown that plunge depth has a strong effect on the formation and shape of the hook defect. Moreover, the fracture behavior of the welds is strongly dependent on the hook defect configuration. By applying the so-called one-factor at a time (OFAT) method combined with macro and microstructure characterization it was possible to identify three possible hook defect configurations. A comprehensive description of the different hook configuration formation is presented by analyzing the microstructure of samples from interrupted welding tests. The configuration of the hook defect depends on the position and direction of the material flow around the sleeve and the drop region. Macro and microstructure analysis of interrupted mechanical test specimens allowed the characterization of the crack initiation site and crack propagation path according to qualitative observations of hook configuration, bonding ligament and the interface region between the heat affected zone and the thermal mechanically affected zone. It was found that the fracture mode is also strongly related to the configuration of the hook defect. The optimized welding condition was reached using intermediate values of plunge depth, which produces a hook pointing down configuration.

Journal ArticleDOI
TL;DR: In this article, the effect of vertical magnetic field on grain size and orientation of ferrite and austenite in welds of 10mm 316L stainless steel were investigated during multilayer narrow gap laser-MIG hybrid welding.

Journal ArticleDOI
TL;DR: In this paper, a basalt-glass hybrid composite has been fabricated and machined using laser beam drilling, to predict a safe machining zone pertaining to high drill quality with minimum heat-affected zone and maximum hole circularity.
Abstract: In the present work, basalt–glass hybrid composite has been fabricated and machined using laser beam drilling, to predict a safe machining zone pertaining to high drill quality with minimum heat-affected zone and maximum hole circularity. The prediction of the zone has been done by mathematical modeling using response surface methodology. The obtained zone has also been validated by performing more experiments. Moreover, the dependency of hole circularity and heat-affected zone on input parameters has also been discussed. From the results, it is evident that the obtained zone is capable of minimizing the heat-affected zone with acceptable hole circularity. Moreover, the behavior of input parameters is non-monotonic in nature.

Journal ArticleDOI
TL;DR: In this paper, the creep behavior of P92 steel welded joint that had experienced creepfatigue (CF) loading at the nanoscale was studied at both as-welded and CF samples.

Journal ArticleDOI
TL;DR: The weldability of GTD-111 nickel-based superalloy by Nd:YAG pulse laser with an average power of 250 W was studied using several pre- and post-weld heat treatment cycle, and the characteristics of liquation, solidification and strain-age cracks were also investigated.

Journal ArticleDOI
TL;DR: In this paper, Ni-based superalloys IN718 and IN713LC have been joined through linear friction welding (LFW) in order to achieve a clean weld region which is free of micro-porosity, micro-cracking and oxides.
Abstract: Ni-based superalloys IN718 and IN713LC have been joined through linear friction welding (LFW) in this study. The variation of microstructure across the weld line developed during linear friction welding and after post weld heat-treatment (PWHT) has been investigated. Their effects on microhardness have also been studied. A clean weld region which is free of micro-porosity, micro-cracking and oxides, was achieved. Dynamic recrystallisation (full and partial) occurred on both sides of the weld, which produced much finer grains in the recrystallised zone. Dissolution of ‘parent’ γʹ/γʹʹ, towards the weld line was observed on each side of the weld. However, reprecipitation of γ′ was only found in the as-welded IN713LC. All these were found to have a huge impact on the hardness profile. A softer heat affected zone (HAZ) was found in the IN718 side with the lowest hardness value achieved at an axial position 0.6 mm from the weld line. The increased dissolution of γ'/γ'' towards the weld line resulted in decreasing hardness towards the weld line. However, the formation of refined grains closer to the weld line increased the hardness towards the weld line from axial position 0.6 mm. In contrast, a harder HAZ was found in the IN713LC side, which resulted from the formation of finer reprecipitated γ′ and recrystallised grains. PWHT brought about reprecipitation and/or further reprecipitation of γʹ/γʹʹ in the IN718 and IN713LC HAZs, resulting in stronger HAZs.

Journal ArticleDOI
TL;DR: In this paper, the implant test was used to study HAC in a quenched and tempered steel S960QL and a high-strength steel produced by thermo-mechanical controlled process S960MC.

Journal ArticleDOI
TL;DR: In this paper, the effects of hybrid laser-arc welding process parameters on the weld formation of a dissimilar steel joint were studied, and a full penetrated weld with minimum defects was obtained under the optimized parameters.
Abstract: Effects of hybrid laser-arc welding process parameters on the weld formation of a dissimilar steel joint were studied. A full penetrated weld with minimum defects was obtained under the optimized parameters. Different thermal conductivities and phase transition temperature resulted in a wider heat affected zone (HAZ) of high-strength low alloy steel (EH36) than that of austenitic stainless steel (316L). Owing to the limited penetration of arc, the laser zone could be only heated by laser while the hybrid zone was heated by not only laser but also arc, resulting in higher heat input and larger grain size in hybrid zone than in laser zone. The addition of filler wire led to higher contents of chromium (Cr) and nickel (Ni) in hybrid zone than laser zone, which inhibited the formation of austenite and led to the formation of martensite in laser zone. Small grain size and existence of martensite resulted in higher hardness of laser zone than hybrid zone. Tensile samples of both laser zone and hybrid zone failed at the EH36 side with massive dimples distributing on the fracture surfaces, indicating good tensile property of the welds and typical characteristics of ductile fracture. Corrosion resistance of laser zone was weaker than that of hybrid zone, which was closely related to the formation of martensite with poor corrosion resistance instead of austenite with good corrosion resistance.

Journal ArticleDOI
TL;DR: In this article, Butt welds of an advanced high strength dual phase steel were fabricated using friction stir welding at a constant rotational speed of 800 rpm and different transverse speeds of 100, 150 and 200 mm/min.
Abstract: In this study, butt welds of an advanced high strength dual phase steel were fabricated using friction stir welding at a constant rotational speed of 800 rpm and different transverse speeds of 100, 150 and 200 mm/min. It was observed that sound welds can be obtained at transverse speeds of 100 and 150 mm/min. At transverse speed of 100 mm/min, the entire stir zone processed at temperatures higher than Ac3. By increasing transverse speed to 150 mm/min, temperature in the bottom region of the stir zone lied between Ac1 and Ac3, while the middle and the top regions experienced temperatures higher than Ac3. The lower peak temperature in the bottom region of the stir zone resulted in finer and harder microstructure. Transmission electron microscopy analysis revealed that the martensite phase partially tempers during non-isothermal tempering of the outer part of the heat affected zone, which gives rise to the softening phenomenon. It was also found that increasing strength of the softened HAZ, decreasing width of the softened HAZ as well as increasing the strength of the stir zone, owing to increasing tool transverse speed, results in higher overall strength and ductility of the joint.

Journal ArticleDOI
01 Oct 2020-Optik
TL;DR: In this paper, a simulation of the continuous disk laser welding process for dissimilar joining between 304 stainless steel and copper is simulated, where six different heat flux distribution models are implemented into Abaqus/Standard solver using additional DFLUX subroutine written in the FORTRAN programming language.

Journal ArticleDOI
TL;DR: In this article, the effect of cooling conditions on the corrosion resistance of joints in 3.5% NaCl solution was investigated using the open circuit potential (OCP), the potentiodynamic polarization, and the corrosion morphology after immersing for different time.

Journal ArticleDOI
Xiaohui Han, Zhibin Yang1, Yin Ma, Chunyuan Shi1, Zhibin Xin1 
TL;DR: In this article, the effects of welding parameters on the porosity distribution and mechanical properties were comprehensively investigated in a 6082-T6 aluminum alloy with thickness of 6mm, where the porosities mainly appeared near the fusion line of the arc zone when the arc current larger than 140 A and which mainly existed in the center of the laser zone with other unsuitable parameters.
Abstract: 6082-T6 aluminum alloy with thickness of 6 mm were welded by laser-MIG hybrid welding. The effects of welding parameters on the porosity distribution, the correlations between the porosity distribution and mechanical properties were comprehensively investigated. The porosities mainly appeared near the fusion line of the arc zone when the arc current larger than 140 A, and which mainly existed in the center of the laser zone with other unsuitable parameters. Adopting low welding speed and setting heat source distance as around 3 mm were beneficial for the reduction of the porosity rate. The laser power, defocus distance, fit-up gap and gas flow rate had less effects on the porosity distribution. The average tensile strength of the joints without porosities was 260 MPa, which decreased to 224 MPa and 202 MPa as the porosity rate increased to 5.1% and 8.9%. The tensile specimens fractured at the heat affected zone or in the weld center when the porosity rates less or greater than 3%, and the fracture feature was diverted from ductile fracture to ductile and brittle mixed mode as the porosity rate increasing. The fatigue strength reduced from 113 MPa to 56 MPa when the porosity rate increased from 0% to 8.9%, while the porosity position had little effect on it. The fracture initiated in the weld surface when the joints without porosity, and which initiated near the porosity when the porosities existed in the joint.

Journal ArticleDOI
TL;DR: In this article, a light duplex Mg-Li alloy LZ91 with a thickness of 3mm was successfully joined by friction stir welding utilizing a tungsten carbide tool.
Abstract: Superlight duplex Mg–Li alloy LZ91 with a thickness of 3 mm was successfully joined by friction stir welding utilizing a tungsten carbide tool. The microstructures in the stir zone showed refined grains consisting of an equiaxed Mg-rich α phase and a Li-rich β phase. The grains in the Mg-rich α phase showed randomized crystal orientations after dynamic recrystallization. Due to the grain refinement and the random orientation of the Mg-rich α phase, the mechanical properties of the stir zone were optimized, and the hardness of the stir zones were higher than that of the base metal. At the same time, the heat affected zone showed no decrease in its strength. Digital image correlation analyses revealed that the strain in the stir zone and base metal were respectively 0.05 and 0.6 before the samples fractured during the joint tensile tests. Therefore, the joints demonstrated 100% tensile efficiency compared with the base metal.

Journal ArticleDOI
TL;DR: In this paper, Inconel 625 nickel alloy and UNS S32205 duplex stainless steel (DSS) were welded with ER2209 filler metal using MIG (Metal Inert Gas) welding method.
Abstract: Inconel 625 nickel alloy and UNS S32205 duplex stainless steel (DSS) were welded with ER2209 filler metal using MIG (Metal Inert Gas) welding method. The weld metal obtained by DSS filler metal was subjected to mechanical and microstructural evaluation. Toughness and hardness properties had been examined by mechanical and microstructural characterization of weld metal, fusion line, and HAZ (Heat Affected Zone) region, and precipitations were investigated by light microscopy (LM), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Corrosion behavior of base metals and face and root of weld metal were examined by using potentiodynamic polarization test. Additionally, detailed elemental analysis and mapping of weld metal with both optical emission spectrometer (OES) and X-Ray spectrometer were attained. Results demonstrate a significant decrease in toughness of the welding due to the presence of Nb and Mo rich intermetallic precipitations in the Inconel HAZ and root region, although there is no significant increase in hardness. Potentiodynamic polarization test shows that the dilution-induced microstructural transformation in the root of weld has the worst corrosion resistance in the weld metal. Therefore, this dissimilar welding does not have optimum properties for neither toughness nor corrosion.

Journal ArticleDOI
TL;DR: In this paper, the effect of severe double shot peening (SDSP) of Peening pre-weldment and post peening weldment on microstructure properties of Ti 6Al-4V and Titanium Grade 2 dissimilar joint made by laser beam welding was investigated.
Abstract: The present investigation deals with the effect of Severe Double Shot Peening (SDSP) of Peening pre-weldment and Post peening weldment on microstructure properties of Ti 6Al-4V and Titanium Grade 2 dissimilar joint made by laser beam welding. Laser beam welding was performed for butt joint configuration. Full depth of penetration was obtained for the laser beam of 1200 W, welding speeds of 250 mm/min and focus distance of 8 mm configuration. Microstructure studies at weld zone and heat affected zone revealed the presence of more amounts of α martensite and B phases. Tensile study displayed that all the failures occurred at the weld zone in both Peening pre-weldment and Post peening weldment of SDSP. X-rays Diffraction analysis showed the slight presence of residual stress in the Post peening weldment of SDSP. Average hardness value of both dissimilar material reached 285 HV. While comparing the hardness at heat affected zone and welded zone, the hardness of welded zone gradually decreased owing to the failure of conversion of α phase into β1/β2 phase. SEM image exhibited the depth of Peening pre-weldment and Post peening weldment weldments of 8 µm and 10 µm respectively which led to the enhancement of hardness value. Further, the coarse grain boundaries, O-phases and α/α′ phases were observed in the heat affected zone. Fracture morphology of tensile samples revealed the inner minor cracks and voids at fusion zone. Moreover, the formation of Cr2N and CrN was not observed in both welded and heat affected zone that improved the better tensile and bending strength.

Journal ArticleDOI
TL;DR: In this paper, electron backscatter diffraction technique was used to study the microstructural changes and texture evolution during underwater friction stir welding of dissimilar 7003/6060 aluminum alloys.
Abstract: Microstructural changes and texture evolution during underwater friction stir welding of dissimilar 7003/6060 aluminum alloys were investigated via electron backscatter diffraction technique. In the stir zone, equiaxed fine grains were formed through continuous dynamic recrystallization. Due to the enhanced cooling rate, the average grain size of the stir zone was much finer than that of normal friction stir welds. In the heat affected zone, static recovery was the main mechanism for microstructure evolution, resulting in similar grain structure as compared with base materials, while the fraction of low angle grain boundary increased. In the thermo-mechanical affected zone, dynamic recovery and partial crystallization took place on the advancing side of 7003, and a mixed grain structure was formed; dynamic recovery was the dominant evolution mechanism on the retreating side of 6060, and the fraction of low angle grain boundary was increased. The texture in the heat affected zone was almost the same as the base material, and simple shear texture B/ B - {112} was formed in the stir zone. With the distance to the weld center decreasing, the texture density of relevant zone decreased.

Journal ArticleDOI
01 Jan 2020
TL;DR: In this paper, the microstructure of welded joints produced by the plasma+MAG (Metal Active Gas) method of S700MC high yield strength steel (700 MPa) was described.
Abstract: The paper describes the microstructure of welded joints produced by the plasma+MAG (Metal Active Gas) method of S700MC high yield strength steel (700 MPa). Welded joints of thermomechanical steel have been made with different values of heat input. The results of metallographic research of welded joints, microstructure of the weld and heat affected zone, hardness distribution and impact toughness are presented. The heat affected zone consists of two sub-zones with different grain size and lowered hardness. The tensile test show that strength of welded joints was slightly reduced and the bending test revealed no crack formation in the weld. The impact toughness of measured welded samples with V-notch in HAZ (heat affected zone) reached high values that are higher comparing to samples with notch placed in the weld area. The investigation results show that the use of plasma concentrated heat source together with MAG welding arc does not significantly change the structure and deteriorate properties of welded S700MC thermomechanically treated high strength steel. The hybrid plasma+MAG welding method has a potential to become a beneficial alternative to other welding processes due to its high efficiency, reduced amount of weld metal content or limited requirements for a preparation of edges of welded joints.

Journal ArticleDOI
TL;DR: In this paper, the microstructure evolution and high-temperature mechanical properties of laser beam welded TC4/TA15 dissimilar titanium alloy joints under different welding parameters were studied.