Friction stir welding of AZ31 magnesium alloy rolled sheets: Influence of processing parameters

The temperature evolution during friction stir welding (FSW) and the resulting residual stresses of AZ31 Mg alloy were studied to get a better understanding of the mechanisms involved in this process. The relationship between the processing parameters, the heat and plastic deformation produced and the resulting microstructure and mechanical properties was investigated. Increasing the shoulder diameter or the tool rotation speed or decreasing the welding speed produced an increase in the heat generated during the process and then promoted grain growth. The temperature distribution on the advancing side and on the retreating side differed, and stress levels were higher on the retreating side. The grain size heterogeneity produced by FSW was not the prevailing cause of failure.AEROMAG Project N°AST4-CT-2005-516152 European Unio

Friction stir welding of AZ31 magnesium alloy rolled sheets: Influence of processing parameters

International audienceThe temperature evolution during friction stir welding (FSW) and the resulting residual stresses of AZ31 Mg alloy were studied to get a better understanding of the mechanisms involved in this process. The relationship between the processing parameters, the heat and plastic deformation produced and the resulting microstructure and mechanical properties was investigated. Increasing the shoulder diameter or the tool rotation speed or decreasing the welding speed produced an increase in the heat generated during the process and then promoted grain growth. The temperature distribution on the advancing side and on the retreating side differed, and stress levels were higher on the retreating side. The grain size heterogeneity produced by FSW was not the prevailing cause of failure

Texture evolution in Nd:YAG-laser welds of AZ31 magnesium alloy hot rolled sheets and its influence on mechanical properties

AZ31 hot rolled magnesium alloy presents a strong basal texture. Using laser beam welding (LBW) as a joining process induces high temperature gradients leading to major texture changes. EBSD was used to study the texture evolution, and tensile tests coupled with speckle interferometry were performed to understand its influence on mechanical properties. The random texture obtained in the LBW fusion zone is mainly responsible for the yield strength reduction.AEROMAG Project N°AST4-CT-2005-516152 European Unio

Texture evolution in Nd:YAG-laser welds of AZ31 magnesium alloy hot rolled sheets and its influence on mechanical properties

International audienceAZ31 hot rolled magnesium alloy presents a strong basal texture. Using laser beam welding (LBW) as a joining process induces high temperature gradients leading to major texture changes. EBSD was used to study the texture evolution, and tensile tests coupled with speckle interferometry were performed to understand its influence on mechanical properties. The random texture obtained in the LBW fusion zone is mainly responsible for the yield strength reduction

Chemical composition of nano-phases studied by anomalous small-angle X-ray scattering (ASAXS)

Anomalous small-angle X-ray scattering (ASAXS) is a technique developed in the 1980s. It offers the opportunity to go further in the investigation of nano-objects by providing chemical information besides characteristic features like size and volume fraction given by classical SAXS. ASAXS is an element-selective technique based on the anomalous variation of the scattering factor near the absorption edge of one chosen element. This technique requires a tunable wavelength of the incident beam that is available on synchrotron radiation sources. In this study, a simple approach is proposed and detailed to extract chemical information from anomalous SAXS data. To illustrate the procedure, two examples are treated by applying this data processing. The first one aims to discriminate between different possible phases in the Y- Ti-O system that may form nano-oxides in oxide-dispersion-strenghtened (ODS) steels, materials for future nuclear plants. The second one deals with the composition of nano- precipitates formed in the diffusion layer of nitrided steels. Such information is of prime importance to evaluate the maximum nitrogen that can be introduced by such a surface treatment and thus the mechanical properties that can be achieved

Assemblage des alliages de magnésium laminés à chaud par soudage friction malaxage et soudage laser : approche expérimentale vers une compréhension des propriétés mécaniques

Pas de table de matière sur le PDFThe challenges of weight reduction in aerospace industry have drawn considerable interest in magnesium alloys technologies. Assessing the efficiency of new joining techniques, such as Laser Beam Welding and Friction Stir Welding is then required. The aim of this study is to investigate the relationship between welding parameters and the resulting microstructure and mechanical properties. It was part of the AEROMAG European Project whose objective was the use of wrought Magnesium alloys in aeronautics. Friction Stir Welds and Laser Beam (Nd:YAG and CO2) Welds were processed using 2 mm thick hot rolled plates of AZ31, AZ61 and WE43 Magnesium alloys. The process window for LBW and FSW was determined. The weld characterisation was focused on AZ31 alloy. A relationship between welding parameters, the temperatures undergone and the weld microstructure was established for each process. FSW induced microstructural changes and complex residual stress distribution, which have a primary influence in FSW mechanical properties. The influence of texture evolution and precipitation evolution on LBW mechanical properties was also determined. Localisation features similar to shear bands were observed in both LBW and FSW. FSW resulted in a dramatic loss in mechanical properties, which could not be recovered after heat treatments, whereas LBW presented after heat treatment mechanical properties similar to those of the base metal. A comparison was made with precipitation hardenened alloys (AZ61 and WE43) mechanical properties. Finally, the potentiality of replacing aluminium alloys with these magnesium alloys was studied.En raison de la faible densité des alliages de magnésium, un intérêt grandissant est apparu pour leur application dans l'industrie aéronautique. De ce fait, il s'est avéré nécessaire de développer l'assemblage de ces matériaux, notamment par des procédés de soudage innovants, tels le soudage par Friction malaxage (FSW) et le soudage laser. Le but de ce projet est d'étudier les relations entre les paramètres de soudage, les températures et les déformations générées et enfin la microstructure et le comportement mécanique des joints soudés. Ce projet fait partie du projet européen AEROMAG qui a pour objectif de promouvoir l'utilisation des alliages de magnésium corroyés dans l'industrie aéronautique. Les alliages étudiés sont l'AZ31, l'AZ61 et le WE43 sous forme de tôles de 2mm d'épaisseur. Le matériau de base présente une forte texture de fibre par rapport au plan basal. Les soudures ont été effectuées par FSW par laser Nd:YAG et par laser CO2. Le domaine de soudabilité opérationnel (DSO) a été déterminé pour chacun des procédés. Ensuite, l'analyse des joints soudés s'est plus spécialement focalisée sur les soudures optimisées d'AZ31. Une relation entre les paramètres de soudage et la microstructure des joints soudés a pu être trouvée. Le procédé de FSW entraîne une évolution de la microstructure et de l'état de contraintes résiduelles qui ont montré une influence déterminante sur le comportement mécanique des joints soudés. En ce qui concerne le soudage laser, l'influence prépondérante se situe dans l'évolution des textures et de l'état de précipitation. Des localisations de déformation assimilables à des bandes de cisaillement ont été identifiées dans chacun des procédés. Une comparaison a été menée en vue d'établir le procédé le mieux adapté à l'assemblage de tôles de magnésium laminées. Le FSW provoque une diminution très importante des propriétés mécaniques et l'utilisation de traitements thermique n'a pas permis de recouvrer les propriétés du matériau de base; tandis que les propriétés mécaniques des joints soudés laser après traitement thermique sont proches de celles du matériau de base. Une comparaison a été effectuée avec les propriétés mécaniques des joints soudés d'alliages de magnésium à durcissement structural (AZ61 et surtout WE43). Enfin, leur potentialité pour remplacer les alliages d'aluminium a été étudiée

Assemblage des alliages de magnesium laminés à chaud par soudage friction malaxage et soudage laser (approche expérimentale vers une compréhension des propriétés mécaniques)

En raison de la faible densité des alliages de magnésium, un intérêt grandissant est apparu pour leur application dans l industrie aéronautique. De ce fait, il s est avéré nécessaire de développer l assemblage de ces matériaux, notamment par des procédés de soudage innovants, tels le soudage par Friction malaxage (FSW) et le soudage laser. Le but de ce projet est d étudier les relations entre les paramètres de soudage, les températures et les déformations générées et enfin la microstructure et le comportement mécanique des joints soudés. Ce projet fait partie du projet européen AEROMAG qui a pour objectif de promouvoir l'utilisation des alliages de magnésium corroyés dans l industrie aéronautique. Les alliages étudiés sont l AZ31, l'AZ61 et le WE43 sous forme de tôles de 2mm d épaisseur. Le matériau de base présente une forte texture de fibre par rapport au plan basal. Les soudures ont été effectuées par FSW par laser Nd:YAG et par laser CO2. Le domaine de soudabilité opérationnel (DSO) a été déterminé pour chacun des procédés. Ensuite, l analyse des joints soudés s est plus spécialement focalisée sur les soudures optimisées d AZ31. Une relation entre les paramètres de soudage et la microstructure des joints soudés a pu être trouvée. Le procédé de FSW entraîne une évolution de la microstructure et de l'état de contraintes résiduelles qui ont montré une influence déterminante sur le comportement mécanique des joints soudés. En ce qui concerne le soudage laser, l influence prépondérante se situe dans l évolution des textures et de l état de précipitation. Des localisations de déformation assimilables à des bandes de cisaillement ont été identifiées dans chacun des procédés. Une comparaison a été menée en vue d'établir le procédé le mieux adapté à l'assemblage de tôles de magnésium laminées. Le FSW provoque une diminution très importante des propriétés mécaniques et l'utilisation de traitements thermique n'a pas permis de recouvrer les propriétés du matériau de base; tandis que les propriétés mécaniques des joints soudés laser après traitement thermique sont proches de celles du matériau de base. Une comparaison a été effectuée avec les propriétés mécaniques des joints soudés d alliages de magnésium à durcissement structural (AZ61 et surtout WE43). Enfin, leur potentialité pour remplacer les alliages d aluminium a été étudiée.The challenges of weight reduction in aerospace industry have drawn considerable interest in magnesium alloys technologies. Assessing the efficiency of new joining techniques, such as Laser Beam Welding and Friction Stir Welding is then required. The aim of this study is to investigate the relationship between welding parameters and the resulting microstructure and mechanical properties. It was part of the AEROMAG European Project whose objective was the use of wrought Magnesium alloys in aeronautics. Friction Stir Welds and Laser Beam (Nd:YAG and CO2) Welds were processed using 2 mm thick hot rolled plates of AZ31, AZ61 and WE43 Magnesium alloys. The process window for LBW and FSW was determined. The weld characterisation was focused on AZ31 alloy. A relationship between welding parameters, the temperatures undergone and the weld microstructure was established for each process. FSW induced microstructural changes and complex residual stress distribution, which have a primary influence in FSW mechanical properties. The influence of texture evolution and precipitation evolution on LBW mechanical properties was also determined. Localisation features similar to shear bands were observed in both LBW and FSW. FSW resulted in a dramatic loss in mechanical properties, which could not be recovered after heat treatments, whereas LBW presented after heat treatment mechanical properties similar to those of the base metal. A comparison was made with precipitation hardenened alloys (AZ61 and WE43) mechanical properties. Finally, the potentiality of replacing aluminium alloys with these magnesium alloys was studied.PARIS-Arts et Métiers (751132303) / SudocSudocFranceF

RESIDUAL STRESS EVOLUTION ANALYSIS IN AZ31 FRICTION STIR WELDS USING X-RAY AND NEUTRON DIFFRACTION.

The challenges of weight reduction in aerospace industry have drawn considerable interest in magnesium alloys technologies. Assessing the efficiency of new joining techniques, as Friction Stir Welding is then required. During Friction Stir Welding, the welding tool motion induces frictional heating and severe plastic deformation. Then, in addition to the microstructure and texture evolutions generally observed, significant residual stresses can result from this process. The Friction Stir Welds have been processed using 2 mm thick hot rolled plates of AZ31 Magnesium alloy. Residual stress analysis was carried out on a Friction Stir Weld processed using optimum welding parameters. Laboratory X-ray diffraction and Neutron diffraction were performed. Indeed, the use of Neutron diffraction was especially interesting because it avoids matter removal required with X-ray technique. Moreover, with Friction Stir Welding, the complex thermo-mechanical input induces complex stress gradients. Then, the high penetration capability of the Neutron diffraction technique was thus essential to allow the determination of stress gradients in a nondestructiv

Influence of the microstructural changes and induced residual stresses on tensile properties of wrought magnesium alloy friction stir welds

Friction stir welding induces a microstructural evolution and residual stresses that will influence the resulting mechanical properties. Friction stir welds produced from magnesium alloy hot rolled plates were studied. Electron back scattered diffraction was used to determine the texture evolution, residual stresses were analysed using X ray diffraction and tensile tests coupled with speckle interferometry were performed. The residual stresses induced during friction stir welding present a major influence on thefinal mechanical properties