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M C Chaturvedi - One of the best experts on this subject based on the ideXlab platform.
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study of the Fusion Zone and heat affected Zone microstructures in tungsten inert gas welded inconel 738lc superalloy
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006Co-Authors: O A Ojo, N L Richards, M C ChaturvediAbstract:The Fusion Zone and heat-affected Zone (HAZ) microstructures obtained during tungsten inert gas (TIG) welding of a commercial superalloy IN 738LC were examined. The microsegregation observed during solidification in the Fusion Zone indicated that while Co, Cr, and W segregated to the γ dendrites, Nb, Ti, Ta, Mo, Al, and Zr were rejected into the interdendritic liquid. Electron diffraction and energy-dispersive X-ray microanalyses using a transmission electron microscope (TEM) of secondary phases, extracted from the Fusion Zone on carbon replicas, and of those in thin foils prepared from the Fusion Zone showed that the major secondary solidification constituents, formed from the interdendritic liquid, were cubic MC-type carbides and γ-γ’ eutectic. The terminal solidification reaction product was found to consist of M3B2 and Ni7Zr2 formed in front of the interdendritic γ-γ’ eutectic. Based on the knowledge of the Ni-Ti-C ternary system, a pseudoternary solidification diagram was adapted for IN 738 superalloy, which adequately explained the as-solidified microstructure. The HAZ microfissuring was observed in regions surrounding the Fusion Zone. Closer and careful microstructural examination by analytical scanning electron microscopy revealed formation of re-solidified constituents along the microfissured HAZ grain boundaries, which suggest that HAZ cracking in this alloy involves liquation cracking. Liquation of various phases present in preweld alloy as well as characteristics of the intergranular liquid film contributing to the alloy’s low resistance to HAZ cracking were identified and are discussed.
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Fusion Zone microstructure of laser beam welded directionally solidified Ni3Al-base alloy IC6
Scripta Materialia, 2006Co-Authors: R.g. Ding, Olanrewaju A. Ojo, M C ChaturvediAbstract:Abstract The Fusion Zone microstructure of laser welded alloy IC6 was examined. Extensive weld-metal cracking was observed to be closely associated with non-equilibrium eutectic-type microconstituents identified as consisting of γ, γ′ and NiMo (Y) phases. Their formation has been related to modification of primary solidification path due to reduced solutal microsegregation.
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Microstructural study of weld Fusion Zone of TIG welded IN 738LC nickel-based superalloy
Scripta Materialia, 2004Co-Authors: O A Ojo, N L Richards, M C ChaturvediAbstract:Abstract The weld Fusion Zone microstructure of a commercial aerospace superalloy IN 738 was examined. Elemental segregation induced interdendritic microconstituents were identified to include terminal solidification product M3B2 and Ni7Zr2 in association with γ–γ′ eutectic constituent, which require proper consideration during the development of optimum post weld heat treatment.
Y. Zhou - One of the best experts on this subject based on the ideXlab platform.
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microstructure hardness relationship in the Fusion Zone of trip steel welds
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: S.s. Nayak, Y. Okita, V Baltazar H Hernandez, Y. ZhouAbstract:Abstract Fusion Zone of three TRIP steels, categorized as AT: C–Mn–Al, AST: C–Mn–Al–Si and ST: C–Mn–Si, in resistance spot welding was characterized with respect to microstructure, phase analysis, and hardness. The Fusion Zone microstructure was found to depend on chemistry: (i) AT steel contained ferrite phase surrounded by bainite and martensite regions, (ii) AST steel showed a bainite structures along with martensite laths and interlath retained austenite, whereas (iii) ST steel constituted single phase martensite laths with interlath austenite. X-ray diffraction study indicated that retained austenite fraction in the Fusion Zone increases with increase in Si content in it. The AST Fusion Zone hardness lies between those of the AT and ST steels; the ST Fusion Zone hardness was higher than that of AT steel because of the single phase martensite microstructure. Comparison of Fusion Zone microstructure and hardness to earlier study on laser welding of the TRIP steels with similar chemistries revealed that higher cooling rate in resistance spot welding led to higher Fusion Zone hardness compared to laser welding; which was attributed either to decrease in softer ferrite phase (AT steel) in the microstructure or refinement of martensite laths (ST steel).
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Microstructure–hardness relationship in the Fusion Zone of TRIP steel welds
Materials Science and Engineering: A, 2012Co-Authors: S.s. Nayak, V. H. Baltazar Hernandez, Y. Okita, Y. ZhouAbstract:Abstract Fusion Zone of three TRIP steels, categorized as AT: C–Mn–Al, AST: C–Mn–Al–Si and ST: C–Mn–Si, in resistance spot welding was characterized with respect to microstructure, phase analysis, and hardness. The Fusion Zone microstructure was found to depend on chemistry: (i) AT steel contained ferrite phase surrounded by bainite and martensite regions, (ii) AST steel showed a bainite structures along with martensite laths and interlath retained austenite, whereas (iii) ST steel constituted single phase martensite laths with interlath austenite. X-ray diffraction study indicated that retained austenite fraction in the Fusion Zone increases with increase in Si content in it. The AST Fusion Zone hardness lies between those of the AT and ST steels; the ST Fusion Zone hardness was higher than that of AT steel because of the single phase martensite microstructure. Comparison of Fusion Zone microstructure and hardness to earlier study on laser welding of the TRIP steels with similar chemistries revealed that higher cooling rate in resistance spot welding led to higher Fusion Zone hardness compared to laser welding; which was attributed either to decrease in softer ferrite phase (AT steel) in the microstructure or refinement of martensite laths (ST steel).
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Microstructure, hardness and tensile properties of Fusion Zone in laser welding of advanced high strength steels
Canadian Metallurgical Quarterly, 2012Co-Authors: A Santillan Esquivel, S.s. Nayak, M S Xia, Y. ZhouAbstract:Fusion Zone (FZ) of advanced high strength steel welds, with similar and dissimilar combinations, in diode laserweldingwascharacterisedinrespecttomicrostructure,microhardnessandtensilestrength.AverageFZ hardness and tensile properties were correlated to the respective microstructure and chemistry. A linear relationship of the FZ hardness with carbon content was observed for all welding combinations; however, carbon equivalent representing all the alloying elements in the FZ showed slightly better linear fit. The plot of calculated martensite hardness and experimental FZ hardness versus carbon content represented three regions: high carbon content, .0?15 wt-%, leads to fully martensitic microstructure with good hardness matching; reducing the carbon content to 0?1–0?15 wt-% resulted in mixed microstructure consisting dominantlymartensitewithfewfractionofferritegivinghardnessvaluejustbelowmartensitehardness;andfor low carbon content the microstructure was dominantly soft ferrite phase causing large deviation from martensite hardness. Fusion Zone tensile strength was observed to follow linear relationship with hardness.
T. Mohandas - One of the best experts on this subject based on the ideXlab platform.
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Studies on Fusion Zone fracture behaviour of electron beam welds of an α+β-titanium alloy
Journal of Materials Science, 1996Co-Authors: T. Mohandas, D. Banerjee, Y. R. Mahajan, V. V. Kutumba RaoAbstract:A study was undertaken to understand the Fusion Zone fracture behaviour of electron beam welded α+β-titanium alloy Ti-6.5 Al-3.3 Mo-1.8 Zr and 0.25 Si. The effect of base metal microstructure, the amount of heat input and post weld heat treatment cycle on the all-weld tensile properties and fracture behaviour was investigated in this work. In general, it was found that the tensile strength and ductility of α+β-base welds are higher than that of the β-base welds and the difference was attributed to the presence of wider Fusion Zone grains of β-base welds. The β-base weld tensile specimens always exhibited an intergranular fracture mode irrespective of the amount of heat input. The single pass low heat input α+β-base welds failed by ductile transgranular fracture mode, while high heat input single pass welds failed by a mixed mode (intergranular plus faceted) fracture. In general high heat input welds showed low ductility mainly on account of the strain localization effects at the grain boundary alpha phase. Post-weld heat treatments of α+β-base welds resulted in the improvement of tensile ductility and were associated with transgranular fracture due to the absence of strain localization effects at the grain boundary alpha phase.
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studies on Fusion Zone fracture behaviour of electron beam welds of an α β titanium alloy
Journal of Materials Science, 1996Co-Authors: T. Mohandas, D. Banerjee, Y. R. Mahajan, V Kutumba V RaoAbstract:A study was undertaken to understand the Fusion Zone fracture behaviour of electron beam welded α+β-titanium alloy Ti-6.5 Al-3.3 Mo-1.8 Zr and 0.25 Si. The effect of base metal microstructure, the amount of heat input and post weld heat treatment cycle on the all-weld tensile properties and fracture behaviour was investigated in this work. In general, it was found that the tensile strength and ductility of α+β-base welds are higher than that of the β-base welds and the difference was attributed to the presence of wider Fusion Zone grains of β-base welds. The β-base weld tensile specimens always exhibited an intergranular fracture mode irrespective of the amount of heat input. The single pass low heat input α+β-base welds failed by ductile transgranular fracture mode, while high heat input single pass welds failed by a mixed mode (intergranular plus faceted) fracture. In general high heat input welds showed low ductility mainly on account of the strain localization effects at the grain boundary alpha phase. Post-weld heat treatments of α+β-base welds resulted in the improvement of tensile ductility and were associated with transgranular fracture due to the absence of strain localization effects at the grain boundary alpha phase.
M Kamaraj - One of the best experts on this subject based on the ideXlab platform.
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laves phase in alloy 718 Fusion Zone microscopic and calorimetric studies
Materials Characterization, 2015Co-Authors: S G K Manikandan, D Sivakumar, M KamarajAbstract:Abstract Microstructural characterization of alloy 718 Fusion Zone welded with both solid solution and age hardenable filler metal has been done. The microsegregation and the aging response were studied by employing three levels of weld cooling rate. Gas Tungsten Arc welding process was used. The Fusion Zone of solid solution filler metal has been responding to the aging treatment due to the weld process conditions and weld metal chemistry. However the weld metal composition was modified due to the higher molybdenum (Mo) content in solid solution filler metal. The effect of this modification on the phase reaction temperatures was studied and the same was compared with the conventional filler metal.
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Laves phase in alloy 718 Fusion Zone — microscopic and calorimetric studies
Materials Characterization, 2015Co-Authors: S G K Manikandan, K. Prasad Rao, D Sivakumar, M KamarajAbstract:Abstract Microstructural characterization of alloy 718 Fusion Zone welded with both solid solution and age hardenable filler metal has been done. The microsegregation and the aging response were studied by employing three levels of weld cooling rate. Gas Tungsten Arc welding process was used. The Fusion Zone of solid solution filler metal has been responding to the aging treatment due to the weld process conditions and weld metal chemistry. However the weld metal composition was modified due to the higher molybdenum (Mo) content in solid solution filler metal. The effect of this modification on the phase reaction temperatures was studied and the same was compared with the conventional filler metal.
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effect of weld cooling rate on laves phase formation in inconel 718 Fusion Zone
Journal of Materials Processing Technology, 2014Co-Authors: S G K Manikandan, D Sivakumar, M KamarajAbstract:Abstract Inconel 718 (2 mm thick) was welded using argon and helium gas shielded tungsten arc welding process with a filler metal. Both constant current and compound current pulse modes were applied and the cooling rates calculated. The dependence of Laves phase formation, dendrite arm spacing and niobium segregation ratios in Fusion Zone on the nature of shielding gases and current was studied. The maximum instantaneous weld cooling rate was achieved for the combination of Helium shielding gas and compound current pulse mode. This ultimately resulted in reduction of laves phase, segregation of niobium and dendrite arm spacing in the Fusion Zone.
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Microstructural characterization of liquid nitrogen cooled Alloy 718 Fusion Zone
Journal of Materials Processing Technology, 2014Co-Authors: S G K Manikandan, K. Prasad Rao, D Sivakumar, M KamarajAbstract:Abstract The interdendritic Laves phase and the microsegregation have been investigated in Alloy 718 Fusion Zone cooled with liquid nitrogen during welding. Conventional GTA welding process was employed with modified waveform and two types of shielding gas and filler metal (solid solution and age hardenable). The weld cooling rate was enhanced using liquid nitrogen cooling during Gas Tungsten Arc welding process. The resultant Fusion Zone microstructures were characterized using the metallurgical tools. Dendrite remelting phenomenon was observed from the optical micrographs. It was found that the enhanced cooling rate with liquid nitrogen reduced the interdendritic phases which were confirmed in both the electron microscopic and the X-ray diffraction analysis. The elemental mapping in scanning electron microscope-energy dispersive spectral analysis also confirmed the reduced microsegregation. The dendrite arm spacing was reduced from the range of 15–54 μm (CCPHE–CCAR, conventional) to 3–17 μm (CCPHE–CCAR, liquid nitrogen cooled) for the employed process variables. The computed weld cooling rate was found to be enhanced from seven to fifteen times than the conventional welding process.
T Domanski - One of the best experts on this subject based on the ideXlab platform.
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numerical prediction of Fusion Zone and heat affected Zone in hybrid yb yag laser gmaw welding process with experimental verification
Procedia Engineering, 2016Co-Authors: Marcin Kubiak, Wiesława Piekarska, Z Saternus, T DomanskiAbstract:Abstract This work concerns mathematical and numerical modelling of temperature field during hybrid welding process using Yb:YAG laser and electric arc in GMAW method. Numerical analysis is performed taking into account the motion of liquid steel in the Fusion Zone. Yb:YAG laser power distribution is determined on the basis of experimental research made on TruDisk 12002 laser. Geostatistical Kriging method is used in the interpolation of Yb:YAG laser power intensity distribution. Temperature field and melted material velocity field in the Fusion Zone of hybrid welded sheets made of S355 steel are obtained on the basis of numerical solution of continuum mechanics equations in Chorin's projection method and finite volume method. Experimental research of laser beam profile is performed in order to verify the correctness of developed heat source model. Fusion Zone and heat affected Zone geometry is predicted on the basis of calculated temperature field in the cross section of hybrid welded joint.
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numerical prediction of Fusion Zone and heat affected Zone in hybrid yb yag laser gmaw welding process with experimental verification
Procedia Engineering, 2016Co-Authors: Marcin Kubiak, Wiesława Piekarska, Z Saternus, T DomanskiAbstract:Abstract This work concerns mathematical and numerical modelling of temperature field during hybrid welding process using Yb:YAG laser and electric arc in GMAW method. Numerical analysis is performed taking into account the motion of liquid steel in the Fusion Zone. Yb:YAG laser power distribution is determined on the basis of experimental research made on TruDisk 12002 laser. Geostatistical Kriging method is used in the interpolation of Yb:YAG laser power intensity distribution. Temperature field and melted material velocity field in the Fusion Zone of hybrid welded sheets made of S355 steel are obtained on the basis of numerical solution of continuum mechanics equations in Chorin's projection method and finite volume method. Experimental research of laser beam profile is performed in order to verify the correctness of developed heat source model. Fusion Zone and heat affected Zone geometry is predicted on the basis of calculated temperature field in the cross section of hybrid welded joint.
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Numerical Prediction of Fusion Zone and Heat Affected Zone in Hybrid Yb:YAG laser + GMAW Welding Process with Experimental Verification
Procedia Engineering, 2016Co-Authors: Marcin Kubiak, Wiesława Piekarska, Z Saternus, T DomanskiAbstract:Abstract This work concerns mathematical and numerical modelling of temperature field during hybrid welding process using Yb:YAG laser and electric arc in GMAW method. Numerical analysis is performed taking into account the motion of liquid steel in the Fusion Zone. Yb:YAG laser power distribution is determined on the basis of experimental research made on TruDisk 12002 laser. Geostatistical Kriging method is used in the interpolation of Yb:YAG laser power intensity distribution. Temperature field and melted material velocity field in the Fusion Zone of hybrid welded sheets made of S355 steel are obtained on the basis of numerical solution of continuum mechanics equations in Chorin's projection method and finite volume method. Experimental research of laser beam profile is performed in order to verify the correctness of developed heat source model. Fusion Zone and heat affected Zone geometry is predicted on the basis of calculated temperature field in the cross section of hybrid welded joint.
