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C.s. Paglia - One of the best experts on this subject based on the ideXlab platform.
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the time temperature corrosion susceptibility in a 7050 t7451 friction stir weld
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: C.s. Paglia, R G BuchheitAbstract:Abstract The temperature gradient occurring for a short time during friction stir welding greatly affects the localized corrosion properties of welded 7050-T7451 plates. An immersion experiment in a salty solution was carried out in order to verify the influence of short-term post-weld heat treatments at temperatures similar to those taking place during friction stir welding on the corrosion behaviour of friction stir welded 7050-T7451. The experiment consisted of inserting thermocouples at different weld regions for the registration of the temperature development with time, and partially immersing the welded plate in a salty solution at 480 °C. In this manner, the weld experienced different temperature expositions at different locations. It was found that a temperature exposition above 180 °C for 20 min significantly increases the general corrosion resistance of friction stir welded 7050-T7451. The re-exposition of 7050-T7451 friction stir weld to a time–temperature combination similar to that occurring during the welding process on the thermomechanically heat affected zones of the weld, significantly improves the corrosion properties and the Environmental Cracking resistance. After the short-term temperature exposition, the fracture location of samples tested in a 3.5 wt.% NaCl solution moved from the corrosion susceptible thermomechanically affected zone to the heat affected zone.
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the influence of artificial aging on the microstructure mechanical properties corrosion and Environmental Cracking susceptibility of a 7075 friction stir weld
Materials and Corrosion-werkstoffe Und Korrosion, 2007Co-Authors: C.s. Paglia, Kumar V Jata, R G BuchheitAbstract:The influence of overaging to the T7451 temper on the microstructure, the mechanical properties, and the corrosion susceptibility of friction-stir-welded 7075 aluminum alloy was investigated by means of transmission electron microscope (TEM), SEM investigations, constant extension rate tests (CERT), alternate immersion tests, and potentiodynamic scans. The overaging that occurs during welding within the heat-affected zones of the friction-stir-welded 7075-O tempered plates promotes a slight formation of intragranular and grain boundary precipitates and increases the mechanical as well as the corrosion resistance properties as compared to the T7451 welded plates. The "double" overaging treatment, consisting of the T7451 temper and the thermal transient experienced by the heat-affected zones of the 7075-T7451 welded plates, increases the size of the intragranular and the grain boundary precipitates as well as the precipitate-free zones. These facts decrease the mechanical and corrosion properties of the 7075-T7451 weld. The T7451 thermal treatment applied after the welding of the 7075-O plates promotes the high presence of small precipitates and reduces the size of the precipitate-free zones. This fact increases the general corrosion resistance, but decreases the mechanical properties. Therefore, the corrosion as well as the mechanical properties are greatly correlated with minute changes in the microstructure, which can arise by short-term heat exposure as for instance during welding. It was also found that the Environmental susceptibility measured by means of CERTs may be influenced by "solution-strengthening" corrosion mechanisms which increase the strain. This fact is present in weld microzones particularly susceptible to corrosion.
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Microstructure, microchemistry and Environmental Cracking susceptibility of friction stir welded 2219-T87
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: C.s. Paglia, Rudolph G. BuchheitAbstract:Abstract The microstructure, the microchemistry and the Environmental assisted Cracking susceptibility was investigated for friction stir welded 2219-T87 plates. It was found that the coarsening of the Al 2 Cu intragranular precipitates occurring within the thermo-mechanically and the heat affected zones after friction stir welding correlates with a decrease in the hardness values. The regions with the lowest hardness are relatively narrow in size and are limited to the boundary between the thermo-mechanically affected zone and the nugget. The weld microzones exhibited a different microstructure but a similar Environmental assisted Cracking susceptibility. The Environmental Cracking susceptibility of the weld was generally low. The constant extension rate tensile tests were carried out in air and in a 3.5 wt.% NaCl solution. For samples tested transverse to the welding direction failure occurred within the thermo-mechanically affected zone–nugget boundary. The thermo-mechanically affected zone–nugget boundary was also the softer region of the weld. The corrosion immersion tests indicated an increased resistance to corrosion for the friction stir welded region as compared to the weld unaffected parent metal.
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a cast 7050 friction stir weld with scandium microstructure corrosion and Environmental assisted Cracking
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: C.s. Paglia, Kumar V Jata, R G BuchheitAbstract:Abstract Microstructure, corrosion and Environmental Cracking behavior of friction stir welded cast aluminum 7050 ingots alloyed with scandium additions was investigated. An over-aged (T7451) and a homogenization (24 h/475 °C) temper were applied to the as-cast plates before friction stir welding, while a post-weld heat treatment was applied to all welds to verify the changes in the corrosion behavior. It was found that the as-cast and heat treated friction stir weld samples exhibited a fully recrystallized equiaxed grain microstructure. The scandium did not significantly dissolve in any of the phases present and remained homogeneously distributed within the matrix. The as-cast friction stir weld microstructure exhibited apart from the nugget region coarse grain boundary phases, wide precipitate-free zones and coarse intragranular precipitates. The post-weld heat treatment (1 h/480 °C–1 h/100 °C boiling water and quench) increased the tensile strength of the as-cast weld, but decreased the strength of the heat treated welds. The heat treatment of the as-cast samples to an overaging (T7451) and homogenization (24 h/475 °C) temper increased the general corrosion susceptibility of the friction stir welds.
R G Buchheit - One of the best experts on this subject based on the ideXlab platform.
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the time temperature corrosion susceptibility in a 7050 t7451 friction stir weld
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: C.s. Paglia, R G BuchheitAbstract:Abstract The temperature gradient occurring for a short time during friction stir welding greatly affects the localized corrosion properties of welded 7050-T7451 plates. An immersion experiment in a salty solution was carried out in order to verify the influence of short-term post-weld heat treatments at temperatures similar to those taking place during friction stir welding on the corrosion behaviour of friction stir welded 7050-T7451. The experiment consisted of inserting thermocouples at different weld regions for the registration of the temperature development with time, and partially immersing the welded plate in a salty solution at 480 °C. In this manner, the weld experienced different temperature expositions at different locations. It was found that a temperature exposition above 180 °C for 20 min significantly increases the general corrosion resistance of friction stir welded 7050-T7451. The re-exposition of 7050-T7451 friction stir weld to a time–temperature combination similar to that occurring during the welding process on the thermomechanically heat affected zones of the weld, significantly improves the corrosion properties and the Environmental Cracking resistance. After the short-term temperature exposition, the fracture location of samples tested in a 3.5 wt.% NaCl solution moved from the corrosion susceptible thermomechanically affected zone to the heat affected zone.
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the influence of artificial aging on the microstructure mechanical properties corrosion and Environmental Cracking susceptibility of a 7075 friction stir weld
Materials and Corrosion-werkstoffe Und Korrosion, 2007Co-Authors: C.s. Paglia, Kumar V Jata, R G BuchheitAbstract:The influence of overaging to the T7451 temper on the microstructure, the mechanical properties, and the corrosion susceptibility of friction-stir-welded 7075 aluminum alloy was investigated by means of transmission electron microscope (TEM), SEM investigations, constant extension rate tests (CERT), alternate immersion tests, and potentiodynamic scans. The overaging that occurs during welding within the heat-affected zones of the friction-stir-welded 7075-O tempered plates promotes a slight formation of intragranular and grain boundary precipitates and increases the mechanical as well as the corrosion resistance properties as compared to the T7451 welded plates. The "double" overaging treatment, consisting of the T7451 temper and the thermal transient experienced by the heat-affected zones of the 7075-T7451 welded plates, increases the size of the intragranular and the grain boundary precipitates as well as the precipitate-free zones. These facts decrease the mechanical and corrosion properties of the 7075-T7451 weld. The T7451 thermal treatment applied after the welding of the 7075-O plates promotes the high presence of small precipitates and reduces the size of the precipitate-free zones. This fact increases the general corrosion resistance, but decreases the mechanical properties. Therefore, the corrosion as well as the mechanical properties are greatly correlated with minute changes in the microstructure, which can arise by short-term heat exposure as for instance during welding. It was also found that the Environmental susceptibility measured by means of CERTs may be influenced by "solution-strengthening" corrosion mechanisms which increase the strain. This fact is present in weld microzones particularly susceptible to corrosion.
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a cast 7050 friction stir weld with scandium microstructure corrosion and Environmental assisted Cracking
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: C.s. Paglia, Kumar V Jata, R G BuchheitAbstract:Abstract Microstructure, corrosion and Environmental Cracking behavior of friction stir welded cast aluminum 7050 ingots alloyed with scandium additions was investigated. An over-aged (T7451) and a homogenization (24 h/475 °C) temper were applied to the as-cast plates before friction stir welding, while a post-weld heat treatment was applied to all welds to verify the changes in the corrosion behavior. It was found that the as-cast and heat treated friction stir weld samples exhibited a fully recrystallized equiaxed grain microstructure. The scandium did not significantly dissolve in any of the phases present and remained homogeneously distributed within the matrix. The as-cast friction stir weld microstructure exhibited apart from the nugget region coarse grain boundary phases, wide precipitate-free zones and coarse intragranular precipitates. The post-weld heat treatment (1 h/480 °C–1 h/100 °C boiling water and quench) increased the tensile strength of the as-cast weld, but decreased the strength of the heat treated welds. The heat treatment of the as-cast samples to an overaging (T7451) and homogenization (24 h/475 °C) temper increased the general corrosion susceptibility of the friction stir welds.
J G Ballesteros - One of the best experts on this subject based on the ideXlab platform.
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influence of residual stresses and strains generated by cold drawing on hydrogen embrittlement of prestressing steels
Corrosion Science, 2007Co-Authors: J Toribio, V Kharin, Diego Vergara, J A Blanco, J G BallesterosAbstract:Abstract Hydrogen embrittlement plays an important role in Environmental Cracking of prestressing steel wires. The ammonium thiocyanate test (ATT) was implemented as a standard for determination of their susceptibility to Environmentally assisted fracture. However, ATT reveals neither how hydrogen induced fracture (HIF) goes on in steel nor the roles of important manufacturing and service factors. To this end, the knowledge of the residual stresses and plastic strains in wires due to cold drawing, as well as the hydrogenation from harsh environments, are the keys to successful predictions of wire lives. This paper advances previous analyses of HIF in cold drawn prestressing wires via numerical modelling, firstly, of the cold drawing process to obtain the distributions of residual stresses and plastic strains, and secondly, of the stress–strain assisted hydrogen diffusion in wires towards creation the conditions for HIF nucleation. Generated results prove the relevant role of residual stress-and-strain field in hydrogen diffusion in the wires, as well as their possible consequences for HIF.
J Toribio - One of the best experts on this subject based on the ideXlab platform.
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influence of residual stresses and strains generated by cold drawing on hydrogen embrittlement of prestressing steels
Corrosion Science, 2007Co-Authors: J Toribio, V Kharin, Diego Vergara, J A Blanco, J G BallesterosAbstract:Abstract Hydrogen embrittlement plays an important role in Environmental Cracking of prestressing steel wires. The ammonium thiocyanate test (ATT) was implemented as a standard for determination of their susceptibility to Environmentally assisted fracture. However, ATT reveals neither how hydrogen induced fracture (HIF) goes on in steel nor the roles of important manufacturing and service factors. To this end, the knowledge of the residual stresses and plastic strains in wires due to cold drawing, as well as the hydrogenation from harsh environments, are the keys to successful predictions of wire lives. This paper advances previous analyses of HIF in cold drawn prestressing wires via numerical modelling, firstly, of the cold drawing process to obtain the distributions of residual stresses and plastic strains, and secondly, of the stress–strain assisted hydrogen diffusion in wires towards creation the conditions for HIF nucleation. Generated results prove the relevant role of residual stress-and-strain field in hydrogen diffusion in the wires, as well as their possible consequences for HIF.
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effect of residual stress strain profile on hydrogen embrittlement susceptibility of prestressing steel wires
2006Co-Authors: J Toribio, V KharinAbstract:Cold drawn wires of eutectoid pearlitic steel are widely used for prestressing concrete structures which usually work in hostile or aggressive environments, so that stress corrosion Cracking of prestressing steel is a problem of major technological concern. In addition, there is general agreement that hydrogen embrittlement (HE) plays an important role in the Environmental Cracking of such a steel due to particular working conditions or to the local electrochemistry in the vicinity of a crack tip. In this framework, the Standard Test in Ammonium Thiocyanate was proposed by the International Federation of Prestressing (FIP) as a suitable experimental method for checking the susceptibility of high-strength prestressing steels to stress corrosion Cracking in general, and particularly to hydrogen embrittlement. In spite of some objections to this standard corrosion test, it is the best suited for steel control and acceptance. However, the main disadvantage of the FIP test is the scattering of the results, which increases as the externally applied stress decreases. It can be caused by the distribution of residual stresses generated in the vicinity of the wire surface during the manufacturing (cold drawing) process.
Rudolph G. Buchheit - One of the best experts on this subject based on the ideXlab platform.
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Microstructure, microchemistry and Environmental Cracking susceptibility of friction stir welded 2219-T87
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: C.s. Paglia, Rudolph G. BuchheitAbstract:Abstract The microstructure, the microchemistry and the Environmental assisted Cracking susceptibility was investigated for friction stir welded 2219-T87 plates. It was found that the coarsening of the Al 2 Cu intragranular precipitates occurring within the thermo-mechanically and the heat affected zones after friction stir welding correlates with a decrease in the hardness values. The regions with the lowest hardness are relatively narrow in size and are limited to the boundary between the thermo-mechanically affected zone and the nugget. The weld microzones exhibited a different microstructure but a similar Environmental assisted Cracking susceptibility. The Environmental Cracking susceptibility of the weld was generally low. The constant extension rate tensile tests were carried out in air and in a 3.5 wt.% NaCl solution. For samples tested transverse to the welding direction failure occurred within the thermo-mechanically affected zone–nugget boundary. The thermo-mechanically affected zone–nugget boundary was also the softer region of the weld. The corrosion immersion tests indicated an increased resistance to corrosion for the friction stir welded region as compared to the weld unaffected parent metal.