Papers by Keyword: Intermetallic Layer

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Authors: N. Grittner, B. Striewe, A. von Hehl, D. Bormann, M. Hunkel, H.W. Zoch, F.W. Bach
Abstract: The combination of different metallic materials enables the design of lightweight structures with tailor-made properties at global as well local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. Whereas titanium alloys show particular high mechanical strength and good corrosion resistance, aluminium alloys provide a considerable lower density and consequently higher potential for weight savings. However, after conventional fusion joining, e.g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties [1, 2]. In contrast, by solid-state joining techniques like co-extrusion these disadvantages can be avoided. Therefore co-extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co-extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. Two different billet variants were examined in the investigations, a titanium-core integrally moulded in the aluminium-billet and titanium-core inserted in a hollow drilled aluminium-billet. Experiments were made with different material combinations, Al99.5 with titanium grade 2 and AlSi1MgMn with Ti6Al4V. Beside mechanical properties of compound the formation of bonding zone are presented.
Authors: R. Sitek, Janusz Kaminski, Marcin Pisarek, Hubert Matysiak, Krzysztof Jan Kurzydlowski
Abstract: The paper presents results of investigations into the structure and corrosion resistance of Ti-Al diffusion layers produced on two phase (a+b) Ti6Al4V alloy by Chemical Vapour Deposition (CVD). The process was carried out in aluminium chloride (AlCl3) mixed with argon atmosphere. Surface topography and microstructure characterization of the coatings were examined by scanning electron microscopy (SEM). The local chemical composition witch 1 μm lateral resolution was measured via EDS. The phase content was investigated by X-ray diffraction and analysis of the chemical composition of the surface by XPS. Corrosion resistance was tested using the potentiodynamic method in 0.1M Na2SO4 and 0.1M H2SO4 solutions at the room temperature. Their resistance to high temperature at atmospheric pressure was tested by 24-hours cycling to 700°C. The results indicate that the layers produced on the Ti6Al4V titanium alloy exhibit a very good adhesion combined with exceptional corrosion resistance, especially high at high temperatures.
Authors: Guang Xin Wu, Jie Yu Zhang, Qian Li
Abstract: The presence of Mg addition in bath has been shown to improve the corrosion resistance of the hot-dip Al-Zn alloy coating while adhesion of coating degrades. And the underlying mechanism of the additive effects was not very clear. In this work, first-principles method has been used to investigate the effect of Mg addition on thickness of Galvalume coating. The optimized geometric configurations, total energy and electronic charge distributions for the Mg substitution in Fe2Al5 and FeAl3 phases were obtained. And results indicated that the most favorable sites for Mg substitution in both Fe2Al5 and FeAl3 phases are Al positions. Bonding energy and charge density results show that the addition Mg could not form Mg-Al bond and has little effect on the thickness of alloy layer.
Authors: Zainuddin Sajuri, Amirhossein Baghdadi, Muhammad Faisal Mahmod, Junaidi Syarif
Abstract: Metallurgical bonded aluminium-copper bi-metal tube has a future prospect as an alternative material to copper in the heat, ventilation and air-conditioning (HVAC) industries. The application of aluminum-copper bi-metallic material is seems practical in maintaining the quality of existing products. However, the mechanical strength and fatigue properties of the bi-metal tubes are unknown. In this study, metallurgical, mechanical and fatigue properties of the copper phosphorous alloy and aluminium-copper bi-metal tubes were characterized through metallographic analysis, tensile, bending and fatigue tests. The results show that there observed a weak and brittle Al-Cu intermetallic compound at the interlayer between Al and Cu. Tensile fracture surface observation revealed that separation of Cu from Al occurred at the interlayer. The bending properties of the tubes were influenced by the amount of volume fraction of Cu in the materials. Three point bending fatigue test results showed that a critical buckling stress is presents for tubes with diameter less than 12.7mm. The aluminium-copper bi-metal tubes show degradation of fatigue strength almost 55% as compared to that of Cu alloy tube.
Authors: Barbara Striewe, Axel von Hehl, Norbert Grittner, Mirko Schaper, Florian Nürnberger
Abstract: The combination of aluminum and titanium alloys allows for designing lightweight structures with tailor-made properties at the macroscopic global as well as at the microscopic scale. In this context both co-extrusion and friction welding offer a great potential for advanced solutions for products with material combinations of aluminum and titanium. While titanium alloys show particular high mechanical strength and good corrosion resistance, aluminum alloys provide a considerable high specific bending stiffness along with low materials costs. Since the mechanical properties of metallic composites highly depend on the existence and formation of the intermetallic layer in the bonding zone compounds were processed by co-extrusion and friction welding and subsequent heat treatment to investigate the strength and the composition of the bonding zone. The results of friction welded samples concerning the intermetallic layer that was formed during heat treatment were compared with those directly after the co-extrusion. In this layer an enrichment of elements which origin from the aluminum alloy, particularly silicon, was observed. The layer was characterized by optical microscopy, scanning electron microscopy as well as electron probe micro analysis. The mechanical properties were determined by tensile tests.
Authors: Elena Muncut, Ion Aurel Perianu, Dan Glavan, Gheorghe Sima
Abstract: The work includes work steps for joining thin sheets with a thickness ranging from1.0 mm (according to EN10327-2004). The study presents the following steps: problems arising from joining with CMT weld-brazing process of galvanized low-carbon steel sheets, used as filler material CuSi3. This is due to the fact that copper induces: grain refinement by lowering the transformation temperature and precipitation hardening after rapid cooling and tempering the theoretical and experimental study of these problems leads to the possibility of combining copper with iron. This is an experiment to investigate the formation of interlayer containing intermetallic compounds, inter layer located between the molten material and the base material. An important part of the study was the optimizing of weld-brazing parameters: welding current, welding speed and dynamic correction factor Ina.Keywords: galvanized sheets steel, joining, weld-brazing CMT, preserving the zinc layer, intermetallic layer.
Authors: Felipe García, Armando Salinas-Rodríguez, Enrique Nava-Vázquez
Abstract: The reaction between solid steel and liquid Al-Zn-Si alloy leads to the formation of a solid intermetallic interfacial layer. In the case of industrial Al-43.5Zn-1.5Si coated steel strips, the thickness of the intermetallic layer is on average 1.35 μm and the kinetics of the reaction is controlled by the effect of Si on Al and Fe diffusivities through the solid intermetallic layer. In this paper it is shown that the thickness of the intermetallic interfacial layer decreases as the Si content in the liquid alloy increases. EDXS microanalysis at the interface of industrial coated steel strips shows that the interfacial intermetallic compounds are chemically similar to those formed in the bulk of Al-43.5Zn-1.5Si liquid baths in continuous coating lines. Differential acid dissolution of the coatings reveals that the intermetallic layer is not planar at the interface with the coating overlay and is formed by grains of different size and chemical composition. Addition of minute quantities of Ti to the Al-Zn-Si liquid alloy causes changes in the morphology of the intermetallic layer and an overall refining of the microstructure.
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