A comparative study of corrosion resistance in welded joints of aluminium alloy AA1100 obtained by friction-stir and gas metal arc welding processes

En este estudio se evaluó el comportamiento a la corrosión de juntas soldadas obtenidas mediante soldadura por fricción-agitación y por fusión al arco eléctrico de aleación de aluminio AA1100. Con el fin de comparar los efectos de ambos procesos sobre la resistencia a la corrosión, se realizaron pruebas en cámara de niebla salina y ensayos de polarización potenciodinámica, usando cloruro de sodio con base en las normas ASTM B117 y ASTM G5, respectivamente. Se analizaron la velocidad de corrosión, pérdida de masa y curvas de comportamiento potenciodinámico. Los análisis fueron complementados con estereología y con observación de las superficies ensayadas por medio de microscopia electrónica de barrido. Los resultados muestran que la corrosión fue localizada en ambos procesos de soldadura, siendo predominante en la región de soldadura para los procesos al arco. Se presentó para el proceso al arco mayores pérdidas de masa y velocidad de corrosión que para el proceso en estado sólido.In this study was evaluated the corrosion behavior of welded joints obtained by electric arc and friction stir welding in AA1100 aluminum alloy with the aim to compare the effects of the process on the corrosion resistance. Tests were performed on salt spray chamber and potentiodynamic polarization test on welded joints based on ASTM B117 and ASTM G5 standards, respectively, using NaCl. The corrosion rate, mass loss behavior and potentiodynamic curves were analyzed. The analyzes were complemented by observation of tested surfaces with stereology and scanning electron microscopy. The results showed that localized corrosion was observed in both processes, which was stronger in the fusion region of welding arc processed samples. Furthermore, this last kind of samples showed higher mass loss and higher corrosion rate than the solid state processed samples

Study of phase transformations by x-ray diffraction and energy dispersive spectrometry microanalysis in welded joints AA5083-H116 with GMAW-P process and shielded gas mixture 80AR19HE1O2

En este trabajo se estudian las transformaciones de fase en las regiones de soldadura de un solo pase de la aleación AA5083-H116 con proceso GMAW-P automatizado, con gas de protección 80Ar19He1O2, material de aporte ER5183 y con diferentes aportes térmicos. La metodología incluyó un análisis previo de resultados de microscopia óptica que permitió identificar cambios morfológicos en la estructura de las regiones en estudio. Se usó simulación termodinámica computacional mediante el método Calphad para obtener los campos de estabilidad de las fases en aleaciones Al-Mg. A través de microscopía electrónica de barrido y espectrometría por dispersión de energías de rayos X, se identificaron, tanto la morfología, como la composición química de los precipitados en las regiones de soldadura. Finalmente, se utilizó difracción de rayos X, permitiendo obtener difractogramas de las regiones bajo diferentes condiciones de soldadura. Los resultados muestran que, con los diferentes aportes térmicos usados, predomina la matriz FCC rica en Al con Mg en solución sólida, mientras variaron las proporciones de precipitados intermedios de segunda fase FeAl6, FeAl y MnAl12 en las regiones de soldadura.In this work we studied the phase transformations in a single pass welding joint of AA5083-H116 alloy using GMAWP automated process, 80Ar19He1O2 shielding gas mixture, ER5183 filler metal and different heat inputs. The methodology included a preliminary analysis using optical microscopy, which identified morphological changes in microstructure of studied welding regions. A series of computational thermodynamic simulations, based on Calphad method, were used to calculate the phase stability fields in Al-Mg alloys. Scanning electron microscopy and energy dispersive spectrometry techniques were used to identify the morphology and the chemical composition of those precipitates found in welded regions. Finally, X-ray diffraction was used to obtain diffraction patterns of the regions under different welding conditions. Under different heat input values, our results showed that Al-rich FCC matrix with Mg in solid solution predominates in the microstructure, whereas, the proportions of secondary phases (FeAl6, FeAl and MnAl12) changed in some regions of the welded joint

Strain analysis of an electromechanical device for force measurement in friction stir welding developed in a universal milling machine /

En este trabajo fue desarrollado el análisis del comportamiento de las deformaciones de un dispositivo electromecánico de medición de fuerzas axiales y horizontales durante el proceso de soldadura por fricciónagitación (SFA). Se detalla la metodología del diseño mecánico del dispositivo y su fabricación. Se realizó simulación computacional de las deformaciones y los esfuerzos involucrados durante la operación usando técnicas de elementos initos con el programa ANSYS®, cuyos resultados fueron comparados con el desempeño real del dispositivo durante la soldadura de una placa de aluminio comercialmente puro. Los resultados mostraron que el intervalo de valores de las deformaciones unitarias simuladas está entre 3,19×10-10 y 3,34×10-3 mm.mm-1, intervalo que tuvo una diferencia menor al 10% con los valores reales medidos. Estos valores sirvieron para validar la posición y precisión de los sensores de deformación (galgas extensiométricas), los cuales son usados para realizar la medida de fuerzas en los sentidos horizontal y vertical durante el proceso SFA.ABSTRACT In this work was analyzed the behavior of strain in an electromechanical device for measuring axial and horizontal forces during friction stir welding (FSW) process. It was described the methodology of mechanical design of the measurement device and its manufacturing. Computer simulation using inite element analysis with ANSYS ® program was used to calculate the strain and stresses involved during operation. Obtained results were compared with the experimental performance of the device during the welding of a commercially pure aluminum plate. The results showed that the range of simulated strain values was between 3.19 × 10-10 and 3.34 × 10-3 mm.mm-1, which had a diference 10% less compared to actual values measured. Obtained values were used to validate the accuracy and the position of strain sensors (strain gages), which were used for measurement of forces in the horizontal and vertical directions of SFA process

Modeling and characterization of as-welded microstructure of solid solution strengthened Ni-Cr-Fe alloys resistant to ductility-dip cracking part I: numerical modeling

This work aims the numerical modeling and characterization of as-welded microstructure of Ni-Cr-Fe alloys with additions of Nb, Mo and Hf as a key to understand their proven resistance to ductility-dip cracking. Part I deals with as-welded structure modeling, using experimental alloying ranges and Calphad methodology. Model calculates kinetic phase transformations and partitioning of elements during weld solidification using a cooling rate of 100 K.s(-1), considering their consequences on solidification mode for each alloy. Calculated structures were compared with experimental observations on as-welded structures, exhibiting good agreement. Numerical calculations estimate an increase by three times of mass fraction of primary carbides precipitation, a substantial reduction of mass fraction of M23C6 precipitates and topologically closed packed phases (TCP), a homogeneously intradendritic distribution, and a slight increase of interdendritic Molybdenum distribution in these alloys. Incidences of metallurgical characteristics of modeled as-welded structures on desirable characteristics of Ni-based alloys resistant to DDC are discussed here202297305CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informação2006/05661-1LNNano/CNPEM/ABTLus; UNICAM

Modeling and characterization of as-welded microstructure of solid solution strengthened Ni-Cr-Fe alloys resistant to ductility-dip cracking part I: Numerical modeling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This work aims the numerical modeling and characterization of as-welded microstructure of Ni-Cr-Fe alloys with additions of Nb, Mo and Hf as a key to understand their proven resistance to ductility-dip cracking. Part I deals with as-welded structure modeling, using experimental alloying ranges and Calphad methodology. Model calculates kinetic phase transformations and partitioning of elements during weld solidification using a cooling rate of 100 K.s(-1), considering their consequences on solidification mode for each alloy. Calculated structures were compared with experimental observations on as-welded structures, exhibiting good agreement. Numerical calculations estimate an increase by three times of mass fraction of primary carbides precipitation, a substantial reduction of mass fraction of M23C6 precipitates and topologically closed packed phases (TCP), a homogeneously intradendritic distribution, and a slight increase of interdendritic Molybdenum distribution in these alloys. Incidences of metallurgical characteristics of modeled as-welded structures on desirable characteristics of Ni-based alloys resistant to DDC are discussed here.202297305LNNano/CNPEM/ABTLusFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2006/05661-1

Modeling and characterization of as-welded microstructure of solid solution strengthened Ni-Cr-Fe alloys resistant to ductility-dip cracking Part II: Microstructure characterization

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)In part II of this work is evaluated the as-welded microstructure of Ni-Cr-Fe alloys, which were selected and modeled in part I. Detailed characterization of primary and secondary precipitates, subgrain and grain structures, partitioning, and grain boundary morphology were developed. Microstructural characterization was carried out using optical microscopy, SEM, TEM, EBSD, and XEDS techniques. These results were analyzed and compared to modeling results displaying a good agreement. The Hf additions produced the highest waviness of grain boundaries, which were related to distribution of Hf-rich carbonitrides. Experimental evidences about Mo distribution into crystal lattice have provided information about its possible role in ductility-dip cracking (DDC). Characterization results of studied alloys were analyzed and linked to their DDC resistance data aiming to establish relationships between as-welded microstructure and hot deformation performance. Wavy grain boundaries, primary carbides distribution, and strengthened crystal lattice are metallurgical characteristics related to high DDC resistance.202307315LNNano/CNPEM/ABTLusFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2006/05661-1

Stacking fault energy measurements in solid solution strengthened Ni-Cr-Fe alloys using synchrotron radiation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The stacking fault energy (SFE) in a set of experimental Ni-Cr-Fe alloys was determined using line profile analysis on synchrotron X-ray diffraction measurements. The methodology used here is supported by the Warren-Averbach calculations and the relationships among the stacking fault probability (alpha) and the mean-square microstrain (<epsilon(2)(L)>). These parameters were obtained experimentally from cold-worked and annealed specimens extracted from the set of studied Ni-alloys. The obtained results show that the SFE in these alloys is strongly influenced by the kind and quantity of addition elements. Different effects due to the action of carbide-forming elements and the solid solution hardening elements on the SFE are discussed here. The simultaneous addition of Nb, Hf, and, Mo, in the studied Ni-Cr-Fe alloys have generated the stronger decreasing of the SFE. The relationships between SFE and the contributions on electronic structure from each element of additions were established. (C) 2012 Elsevier B.V. All rights reserved.5587075Brazilian Nanotechnology Laboratory LNNano-CNPEM/ABTLuSConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2006/05661-1

Stacking Fault Energy Measurements In Solid Solution Strengthened Ni-cr-fe Alloys Using Synchrotron Radiation

The stacking fault energy (SFE) in a set of experimental Ni-Cr-Fe alloys was determined using line profile analysis on synchrotron X-ray diffraction measurements. The methodology used here is supported by the Warren-Averbach calculations and the relationships among the stacking fault probability (α) and the mean-square microstrain (&lt;ε 2 L&gt;). These parameters were obtained experimentally from cold-worked and annealed specimens extracted from the set of studied Ni-alloys. The obtained results show that the SFE in these alloys is strongly influenced by the kind and quantity of addition elements. Different effects due to the action of carbide-forming elements and the solid solution hardening elements on the SFE are discussed here. The simultaneous addition of Nb, Hf, and, Mo, in the studied Ni-Cr-Fe alloys have generated the stronger decreasing of the SFE. The relationships between SFE and the contributions on electronic structure from each element of additions were established. © 2012 Elsevier B.V.5587075Galen H, F., (2006) JOM, 58 (9), pp. 28-31Bowman, R., (2004) JOM, 56 (9), pp. 7-12Donachie, M., Donachie, S., (2002), p. 439. , Superalloys, A Technical Guide, 2nd edCollins, M.G., Ramirez, A.J., Lippold, J.C., (2004) Weld. J., 83, pp. 39s-49sRamirez, A.J., Lippold, J.C., (2004) Mater. Sci. Eng. A, 380, pp. 259-271Ramirez, A.J., Sowards, J.W., (2006) J. Mater. Process Technol., 179 (20), pp. 212-218Noecker, F.F., Dupont, J.N., (2009) Weld. J., 88 (3), pp. 62s-77sRogers, H.C., (1967) Ductility, p. 55Hull, D., Bacon, D.J., (2001), p. 11. , Introduction to Dislocations, 4th edFrommeyer, G., Brüx, U., Neumann, P., (2003) ISIJ Int., 43 (3), pp. 438-446Grässel, O., (1997) J. de. Phys. IV, 7 (C5), pp. 383-388Ruff, A.W., (1970) Metall. Trans., 1 (9), pp. 2391-2413Reed, R.P., Schramm, R.E., (1974) J. Appl. Phys., 45 (11), pp. 4705-4711Schramm, R.E., Reed, R.P., (1975) Metall. Trans. A, 6, pp. 1345-1351Stokes, A.R., (1948) Proc. Phys. Soc., 61, p. 382Warren, B.E., Warekois, E.P., (1955) Acta metall., 3, pp. 473-479Sambongi, T., (1965) J. Phys. Soc. Jpn., 20 (8), pp. 1370-1374Cheary, R.W., Coelho, A.A., (1996), http://www.ccp14.ac.uk/tutorial/xfit-95/xfit.htmCheary, R.W., Coelho, A., (1992) J. Appl. Crystallogr., 25, pp. 109-121Balzar, D., Ledbetter, H., (1993) J. Appl. Crystallogr., 26, pp. 97-103Balzar, D., (1992) J. Appl. Crystallogr., 25, pp. 559-570Warren, B.E., Averbach, B.L., (1950) J. Appl. Phys., 21, pp. 595-599Schafler, E., (1999) Phys. Status Solidi (a), 175 (2), pp. 501-511Halder, S.K., De, M., Gupta, S.P., (1977) J. Appl. Phys., 48 (8), pp. 3560-3565Chattopadhyay, S.K., Chatterjee, S.K., (1990) J. Mater. Res., 5 (10), pp. 2120-2125Alvin Borges, J.F., Padilha, A.F., Imakuma, K., (1986) Rev. Fis. Apli. Instrum., 1 (4), pp. 1-12Martinez, L.G., Imakuma, K., Padilha, A.F., (1992) Mater. Technol. Steel Res., 63 (5), pp. 221-223Duval, S., Chambreland, S., Caron, P., Blavette, D., (1994) Acta Metall. Mater., 42 (1), pp. 185-194Bower, D.I., Claridge, E., Tsong, I.S.T., (1968) Phys. Status Solidi (b), 29 (2), pp. 617-625Ledbetter, H.M., (1985) J. Appl. Phys., 57 (11), pp. 5069-5070di Masso, L., (1996) J. Phys. IV Suppl. au. J. Phys., 111 (6), pp. 247-250. , C8Glatzel, U., FeUer-Kniepmeier, M., (1991) Scr. Metall. Mater, 25, pp. 1845-1850Symons, D.M., (1997) Metall. Mater. Trans. A, 28 (3), pp. 655-663Siegel, D.J., (2005) Appl. Phys. Lett., 87, p. 121901Tiearney, T.C., Grant, N.J., (1982) Metall. Trans. A, 13, pp. 1827-1836Pettinari, F., (2002) Mat. Sci. Eng. A, 325, pp. 511-519Vanderschaeve, G., Escaig, B., (1978) J. Phys. Lett., 39 (15), pp. 74-77Gallagher, P.C.J., (1970) Met. Trans., 1, pp. 2429-2461Viatte, T., (1996) J. Phys. IV C8 Supp. au. J. Phys., 111 (6), pp. 743-746Zimina, L.N., Burova, N.N., Makushok, O.V., (1986) Met. Sci. Heat Treat., 28 (2), pp. 130-135Kotval, P.S., Venables, J.D., Calder, R.W., (1972) Metall. Trans., 3 (2), pp. 453-458Yukawa, N., (1986) High temperatures alloys for gas turbines and other applications, (PART II), pp. 935-938Tiwari, G.P., Ramanujan, R.V., (2001) J. Mat. Sci., 36, pp. 271-28