Master's thesis deals with consideration possibility of conventional and unconvetional welding methods of wrought magnesium alloys. Methods of Friction Stir Welding, Pulsed Nd:YAG laser and Continuous Fiber laser was used to join magnesium alloy sheets AZ31, AZ61, ZE10 and ZE41. For studying influence of processing parameters on microstructure and mechanical properties were used methods of light microscopy, scanning electron microscopy, tensile tests and microhardness measurements. The results of tensile tests show that from the point of view of keeping ultimate tensile strength is the best methods for welding magnesium alloys Friction Stir Welding. Compared with Nd:YAG laser, fiber laser give better properties of welds. From comparing microstructure and mechanical properties . It wasn't found publications about Friction Stir Welding of magnesium ZE alloys or about FSW sheets with thickness only 0,8 mm and 1,6 mm.

Casting, Solidification, Aluminum, Physical Metallurgy, Mechanical Metallurgy, Strengthening Model, Aluminum Wrought Alloys, Aluminum 7xxx Series, Al-Zn-Mg-Cu / Over the past decades, researchers in casting fields, especially in semi-solid metal state, have endeavored to find new ways to enable the Al wrought alloys of casting using the conventional casting processes; mainly in order to improve the product properties and decrease the product cost. The thixoforming and rheocasting processes have been presented as ways by which the microstructure of Al-base wrought alloys can be changed into non-dendritic, which in turn can lead to improvement to the mechanical properties. This can be because the effect of the non-dendritic microstructure on the mechanical properties of the material. Unfortunately, these processes have proved to be cost prohibitive and be a bit complicated for commercial applications. Further, conventional casting of Al-base wrought alloys along with their superior properties and performance have been a challenge for foundry industry due to the main disadvantage of hot tearing or hot cracking during solidification process. This can render the cast component ineffective. To overcome the disadvantages of thixoforming and rheocasting processes, Controlled Diffusion Solidification (CDS) process was innovated mainly to enable casting of aluminum wrought alloys with a non-dendritic morphology of the primary Al phase in the resultant cast microstructure and thus alleviating the problem of hot tearing and obtaining a cost effective product with improved mechanical properties. The CDS is a simple process involving mixing of two precursor alloys of different thermal masses (temperature and solute) and subsequently casting the resultant mixture of the desired solute composition and temperature as a near net shaped cast product. The process can easily be commercialized with a marginal capital cost required for set up such as the addition of an extra holding furnace. Further, the CDS process would prove itself to be unique in its ability to cast Al-based wrought alloys into near net shaped components without additional processes and cost. The originality of this study is to present a viable casting process for the Al-7xxx wrought alloys (Al-Zn-Mg-Cu); by which the Al-7xxx family alloys are presented in cast condition to have an acceptable uniaxial property range that is comparable with their wrought counterparts. This study presents the process and alloy parameters necessary for the casting of Al-7xxx wrought alloys (Al-Zn-Mg-Cu), by using the CDS process coupling with tilt pour gravity casting (TPGC) machine. The uniaxial tensile mechanical properties of several Al-7xxx CDS castings under various heat treatment conditions, namely, solutionizing (T4), peak aged (T6) and annealing (O), necessary for development of an ageing process on the material were investigated and presented. The tilt pour gravity casting process coupled with the CDS technology was employed to demonstrate the ability to cast Al-7xxx wrought alloys into high integrity components with high strength and ductility. The microstructure characterization was carried out by Electron Microscopy (TEM, SEM and EDS) and DSC test experiments for all the as cast (F), T4, T6 and anneals (O) conditions of the CDS cast components. Also, the predictive capabilities for the yield strength of Al 7xxx alloys CDS cast components was investigated using structural-properties modeling for the various strengthening effects that are recently proposed specifically for the Al-7xxx wrought counterparts. The study has successfully led to a more in-depth understanding of the innovative CDS casting process by applying it to several compositions of Al-7xxx wrought alloys in an industrial scale CDS casting experiments, using tilt pour gravity casting (TPGC) machine. This will hopefully lead us to a clearer path towards commercializing the CDS process and obtaining a viable casting process for Al-base wrought alloys into near net shape components without much change to economics of the casting process. / Dissertation / Doctor of Philosophy (PhD) / Casting, Solidification, Aluminum, Physical Metallurgy, Mechanical Metallurgy, Strengthening Model, Aluminum Wrought Alloys, Aluminum 7xxx Series, Al-Zn-Mg-Cu

L’art de la Serrurerie en Bretagne aux XVIIe et XVIIIe siècles met en lumière l’art du fer forgé, un domaine des arts décoratifs aux confluents de ceux de l’architecture, du mobilier et de l’ornement, devenu, au fil du temps, la « Cendrillon des arts ». Les recherches en archives et les enquêtes sur le terrain inédites ont été menées sur les cinq diocèses (Finistère, Côtes-d’Armor, Morbihan, Ille-et-Vilaine et Loire-Atlantique) qui composent la province de Bretagne avant la Révolution et ont donné lieu à une synthèse historique et artistique développée sur trois axes. La première partie analyse le cadre d’origine et l’évolution des communautés de serruriers en Bretagne à partir de l’étude des chartes et des statuts et de leur application. La deuxième partie s’intéresse à la connaissance de l’individu-serrurier dans son environnement socio-familial, mais également à travers sa formation artisanale et les étapes marquantes de sa vie professionnelle (apprentissage, compagnonnage et maîtrise). La troisième partie examine les commanditaires, le processus de la commande et la production des œuvres – clef, serrure, grille, heurtoir, balcon, rampe…- depuis l’atelier jusqu’aux édifices bretons où certaines d’entre elles demeurent encore. Le catalogue des œuvres ainsi que le dictionnaire biographique (1200 notices) illustrent et proposent des outils documentaires complémentaires à l’étude sociale et culturelle ainsi qu’à l’histoire du goût afin de contribuer à la redécouverte des serruriers bretons tout autant que de leurs œuvres pendant une période considérée, en France, comme l’âge d’or du fer forgé. / The Art of Locksmithery in Britany in the 17th and 18th centuries highlights the art of iron forged – a section of the decorative arts in between architecture, furniture design and ornament that has become the “Cinderella of arts” over the ages.Records based research and on-site investigations were conducted in five dioceses - Finistère, Côtes-d’Armor, Morbihan, Ille-et-Vilaine and Loire-Atlantique, which Britany included before the French Revolution- and resulted in a synthetic essay about history and art. The first part analyses the original background and the evolution of the community of locksmiths in Britany from the study of charters, statuses and their application. The second part presents individual locksmiths in their social and family environment as well as through their training as craftsmen with the main steps of their professional life – apprenticeship, companionship and mastering. The third part deals with the contractors, the ordering process and the creation of pieces of work - key, lock, knocker, grille, balcony, bracket, lectern... - from the workshop to the Breton buildings, a few of which still feature some of those creations.The works catalogue and the biographical dictionary (1200 entries) illustrate and offer other documenting tools for further social and cultural studies and knowledge of design history in order to contribute to the rediscovery of Breton locksmiths and their works over a period regarded as the French golden age of ironwork.

The objective of this research is to increase the understanding of the solidification behaviour of some industrially important wrought aluminium alloys. The investigation methods range from direct investigations of as-cast ingots to laboratory-scale techniques in which ingot casting is simulated. The methods span from directional solidification at different cooling rates to more fundamental and controlled techniques such as DTA and DSC. The microstructure characteristics of the castings have been investigated by optical and Scanning Electron microscopy. Hardness tests were used to evaluate the mechanical properties. The effects of adding alloying elements to 3XXX and 6XXX aluminium alloys have been studied with special focus on the effects of Zn, Cu, Si and Ti. These elements influence the strength and corrosion properties, which are important for the performance of final components of these alloys. Solidification studies of 0-5wt% Zn additions to 3003 alloys showed that the most important effect on the microstructure was noticed at 2.5 wt% Zn, where the structure was fine, and the hardness had a maximum. Si addition to a level of about 2% gave a finer structure, having a relatively large fraction of eutectic structure, however, it also gave a long solidification interval. The addition of small amounts of Cu, 0.35 and 1.0 wt%, showed a beneficial effect on the hardness. Differences have been observed in the ingot surface microstructures of 6xxx billets with different Mg and Si ratios. Excess Si compositions showed a coarser grain structure and more precipitations with possible negative implications for surface defect formation during DC casting. The comparison of alloys of different Ti content showed that the addition of titanium to a level of about 0.15 wt% gave a coarser grain structure than alloys with a normal Ti content for grain refinement, i.e. < 0.02 wt%, although a better corrosion resistance can be obtained at higher Ti contents. The larger grain size results in crack sensitivity during DC casting. A macroscopic etching technique was developed, based on a NaOH solution, and used in inclusion assessment along DC cast billets. Good quantitative data with respect to the size and spatial distribution of inclusions were obtained. The results from studied billets reveal a decreasing number of inclusions going from bottom to top, and the presence of a ring-shaped distribution of a large number of small defects in the beginning of the casting. The present study shows how composition modifications, i.e. additions of certain amounts of alloying elements to the 3xxx and 6xxx Al alloys, significantly change the microstructures of the materials, its castability, and consequently its mechanical properties / QC 20100901

Le patrimoine ferroviaire français comporte de nombreux ponts métalliques, principalement construits au cours de la seconde moitié du XIXème siècle. Ces ouvrages d'art sont donc en service depuis plus d’un siècle et nécessitent une politique de maintenance adaptée. En collaboration avec SNCF Réseau, cette thèse de doctorat apporte des éléments de compréhension sur le comportement mécanique des assemblages rivetés à chaud sous sollicitations monotones et cycliques. Une stratégie expérimentale a été mise en oeuvre afin d'identifier les mécanismes de ruine des assemblages rivetés. Dans un premier temps, le matériau objet de cette étude, un fer puddlé, a été extrait d'éléments provenant du pont sur l'Adour à Bayonne (1864-2013). Ce matériau a été notamment caractérisé sous chargements monotones et cycliques ; sa fragilité, son anisotropie et son comportement dispersif ont été mis en évidence et analysés. Des outils numériques ont été développés pour l’étude microscopique de cette famille de matériaux. Des éprouvettes rivetées de type détail constructif ont par la suite été conçues, fabriquées et testées sous chargements monotones et cycliques. Un scénario précis du fonctionnement et de ruine d'un assemblage mono-rivet en double recouvrement a pu être identifié. Pour cela, les influences des caractéristiques matériau, des concentrations de contraintes, du cisaillement du rivet et de l'effort de serrage ont été étudiées. Les résultats de ce travail, comparés à ceux de la littérature et aux standards de dimensionnement des structures métalliques, montrent la complémentarité d'une étude à plusieurs échelles (comportement matériau et étude locale du fonctionnement des assemblages) dans le but de comprendre et estimer le comportement des structures rivetées anciennes. / Numerous metallic bridges can be found in the French railway heritage. Since a majority of these structures was built during the second half of the 19th century, they have been in service for over a hundred years and need an adapted maintenance policy.These doctoral thesis, done in collaboration with SNCF Réseau, improves the understanding of the mechanical behaviour of hot riveted assemblies under monotonic and cyclic loadings. An experimental strategy was proposed and carried out in order to identify the failure mechanisms of riveted assemblies. First, the studied material, a puddled iron, was obtained from recovered elements from the bridge over the Adour river in Bayonne (1864-2013). Mechanical testing and characterisation was performed under monotonic and cyclic loadings. Puddled iron’s brittle, anisotropic and scattered behaviour was observed and analysed. In-house software applications were developed in order to study this kind of material. Additionally, hot riveted specimens (constructional details) were designed, manufactured and tested under monotonic and cyclic loadings. A precise working (and failure) scenario of the double shear mono-rivet assembly was identified. The influence of the material’s behaviour, stress concentrators, shearing of the rivet and clamping force of the rivet were studied. The results obtained during these research works, compared to the ones found in academic literature as well as construction norms for metallic structures, showed the importance and complementarity of a multi-scale approach (material behaviour and local study of assemblies) in order to understand and assess the behaviour of ancient riveted structures.

The capabilities of various metal Additive Manufacturing (AM) processes, such as Powder Bed Fusion – Laser (PBF-L) and Direct Energy Deposition (DED) are increasing such that it is becoming ever more common to use them in industrial applications. The ability to print atop a substrate broadens that scope of applications. There is ongoing research regarding the mechanical properties of additively processed materials, but little regarding the interaction between additive material and its substrate. An understanding of the mechanical and performance properties of the AM/substrate interface is imperative. This paper describes a study of the strength properties of AM/substrate interfaces, with respect to torsion and tension, and compares them to their fully wrought and fully additive counterparts. PBF-L and DED are used to produce tensile and torsion test specimens of two different materials, SS316L and M300 steels. This provides sufficient variety in testing for a confident analysis to be made.

The main goal of this diploma thesis is the examination of the influence of structure directionality on fatigue properties of formed aluminium alloy 6082/T6. The main attention is focused on the study of the influence of structure directionality on kinetics of short fatigue cracks growth. The measurement of short fatigue cracks growth was performed on cylindrical samples. The samples were made in two different directions; one parallel with the forming direction and second perpendicular to the forming direction. Servo hydraulic machine MTS 880 was used for the cyclic loading. The samples were cycled at two different constant stress amplitudes. Cyclic loading was systematically interrupted in order to measure the length of short cracks by a light microscope. Tensile tests, measuring of cycling hardening-softening curves, observation of microstructure, observation of surface relief, measuring of microhardness and fractographical analysis of fracture surfaces were used for further examination of the influence of the structure directionality. Some of these measured characteristics did not show any influence of the structure directionality (microhardness, fatigue life curve, Young modulus). In other cases is this influence measurable, however insignificant (yield stress, ultimate stress, cyclic hardening-softening curves and kinetics of short fatigue cracks growth). It can be summarised that the material, though the directionality of its microstructure is apparent, shows relatively isotropic mechanical behaviour.

The aim of this master’s thesis is electrochemical characteristics evaluation of magnesium alloys. The theoretical part describes the properties of magnesium and its alloys and their corrosion characteristics. In the experimental part are presented results of corrosion resistance measurement of two types of wrought magnesium alloys. It was AZ31 and AZ61 magnesium alloys, which were measured in Hank’s solutions with addition of ions Ca2+ and Mg2+ (SBF+) and without addition of the ions (SBF). The solution temperature during the measurement was 37 ± 1 °C. The experiments were used electrochemical impedance spectroscopy (EIS) and potentiodynamic tests using linear polarization (LP). EIS measurements were done in times of 5 minutes, 1, 2, 4, 8, 12, 24, 48, 72, 96 and 168 hours. Potentiodynamic tests were only short-term and they started after 5 minutes of stabilization. Both methods were used for measuring the electrochemical characteristics of polished and ground surface of the samples. The most important measurement results were polarization resistance, corrosion potential and corrosion current density. The electrochemical measurements are used to estimate the chemical composition influence and alloy’s structure of the corrosion resistance.

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