Papers by Keyword: Aluminium

Abstract: Aluminium metal matrix composites (AMC) are perspective materials for a wide range of applications in automotive, aerospace and other industries where material mechanical properties and weight ratio is crucial. In AMC manufacturing through metallurgical process the main obstacle for particle introduction into the melt is poor particle wettability and their tendency to form agglomerates due to van der Waals and interfacial forces. Most of currently used AMC manufacturing methods through metallurgical route are effective only for small quantities or are time consuming, even though metallurgical AMC production route would promise significant cost savings. In this study we propose a permanent magnet stirring technology developed by IP UL as tool for alternative realization of stir- and compo-casting methods for AMC production. First results of contactless stirred semi-solid aluminium alloys show effective alloy stirring in melt volume and intense surface deformations that can break the oxide layer and stir in the reinforcement material from the melt surface.

Abstract: Resistance spot welding has significant role in the joining technologies of automotive industry. In the recent period there were some rival technologies, but resistance spot welding remains important. This has numerous reasons however mass production is one of the main motivations. The applied base materials both steel and aluminium develop rapidly. The dual-phase (DP) steels with different strength are typical in the automotive chassis, and the high strength aluminium alloys also continuously spread. These special material combinations mean new challenges for joining technologies, sometimes hybrid aluminium - steel joints should be prepared. In this paper hybrid joints between DP800 steel and 5754-H22/6082-T6 sheets were prepared. The microstructural and strength properties of the joints were investigated and compared. An intermetallic compound was formed between the dissimilar sheets during welding which is basically determine the joint properties.

Abstract: Laser diffraction, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were employed to characterize the particle size, morphology and structure of mechanically alloyed Ti₅₀Al₃₀Ni₂₀ alloy. Cyclic amorphous-crystalline-amorphous phase transformations were investigated during mechanical alloying, using high-energy ball milling technique. After 20 h of milling, an amorphous/nanocrystalline phase was obtained. This amorphous/nanocrystalline phase tended to transform into crystalline grains after 50 h of milling. In a cyclic phase transformation, the obtained crystalline phase is transformed into the amorphous phase after 70 h of milling. This amorphous phase crystallized through a single sharp exothermic peak at 590°C. On the basis of our results, the destabilizing effect of the defects created by the milling media (balls), which leads to the cyclic transformations, depends on the input energy and milling time.

Abstract: Although rigid foam core structures have gotten a lot of attention, there have only been a few researches on foam reinforced sandwich panels with aluminum alloy A6061 sheets as face-sheets. In this research, the sandwich concept was applied to develop lightweight panels for roofing system. Analysis on the influences of core thickness, density, and foam layer arrangement on energy absorption, bending strength and displacement of sandwich panel under the quasi-static three-point bending test were investigated. Sandwich panel core is made of closed-cell polyurethane foam with densities of 40 kg/m³, 60 kg/m³, and 80 kg/m³. The quasi-static three-point bending tests were conducted in accordance to ASTM C-393 Standard and the polyurethane foam cores are design accordingly to the guideline of National Institutes of Standards and Technology (NIST). Load–displacement curves and mechanical properties are shown using data from experimental works. Results demonstrate that increased in thickness of the sandwich panel, also increased the bending strength, energy absorption and displacement. Furthermore, the sandwich panel with 50 mm thickness and 60 kg/m³ density foam core has the maximum bending strength.

Abstract: The research on transparent heater (Thf) films rapidly increases due to their unique photoelectric properties, leading to new generation of optoelectronic device. Here, we report a simple method to fabricate transparent heater based on Al-doped SnO₂ (ASO) thin films. ASO films with 5 wt% Al as dopant were synthesized with various deposition times, namely, 5, 10 and 15 minutes using ultrasonic spray pyrolysis method. The correlation of deposition time on their structural characteristic, optical, electrical and thermal properties has been investigated. X-ray diffraction studies found that all samples exhibit tetragonal structure with preferred orientation along (110) plane. Meanwhile, the UV-Vis transmittance indicated that the sample having good optical transparency in visible light spectrum with the average transmittance up to 89.7%. The sheet resistance of ASO thin films was found to decrease as the deposition time increases to 10 minutes. Furthermore, Al-doped SnO₂ based transparent heater prepared with 10 minutes deposition time presents the excellent thermal temperature up to 76.3 °C at the applied voltage of 20 volt. The above findings reveal that Al-doped SnO₂ can be used as an alternative compound to substitute higher cost indium tin oxide as transparent heater. Keywords: aluminium, composite, spray pyrolysis, SnO₂, transparent heater

Abstract: Carbide tools with mono/multilayer coating such as TiN, TiC, TiAIN, TiB₂ and Al₂O₃ on inserts of WC-Co generated key success for machining of ferrous materials without coolant/lubrication. So far dry machining of aluminium, manufacturing industries such as automobile and aerospace engineering are facing considerable challenges. Exploration of correct cutting tool for machining of aluminium still persists in the present day context. This paper experimentally investigated the affinity and performance of different cutting tool materials available in local tool shopping center along with the diamond coated tool insert prepared and developed in our own HFCVD reactor for machining of aluminium in dry condition. Finally it is revealed that, due to the low chemical affinity, small magnitude of cutting force, chemical inertness and remarkable anti-welding characteristics, diamond coated tool displayed improved performance as compared to other tools.

Abstract: With the enhancement in science and technology, necessity of complex shapes in manufacturing industries becomes essential for more versatile applications. These lead to demand for light weight and durable materials for applications in aerospace, defence, automotive, as well as sports and thermal management. Due to its high-tech structural, functional applications like defence, automobile, aerospace, thermal sensitive materials. Al-Matrix composites are considered as one of those classes of advanced engineering materials. In the present study, Al-RHA (Rice Husk Ash) composites are prepared by powder metallurgy route using 10% and 15% RHA by weight as reinforcement. Presence of abrasive particles leads to difficulty of conventional machining on Al-RHA composites hence non-conventional machining WEDM (Wire-Electric Discharge Machining) has been investigated. Suitable machining parameters for composites using wire EDM have been tried to get maximum material removal rate and speed. Optimizations of experimental parameters have been studied using Taguchi and Anova to standardize the process parameters for machining. Prime process parameters like servo-voltage, pulse-on time and pulse-off-time have been taken into consideration to study cutting quality of Al-RHA Metal matrix Composite using cutting speed as response parameters while effect of RHA weight fraction addition is also considered for evaluation to understand its influence on affecting the response.

Abstract: Our investigations show that electrochemical corrosion of copper is faster than electrochemical corrosion of aluminium at temperatures below 100°C. Literature data analysis shows that the Al atoms diffuse faster than the Cu atoms at temperatures higher than 475°C, Al rich intermetallic compounds (IMCs) are formed faster in the Cu-Al system, and the Kirkendall plane shifts toward the Al side. Electrochemical corrosion occurs due to electric current and due to diffusion. An electronic devise working time, for example, depends on initial copper cover thickness on aluminium wire, connected to the electronic devise, temperature, and volume and dislocation pipe diffusion coefficients, so copper, iron, and aluminium electrochemical corrosion rates are investigated experimentally at room temperature and at temperature 100°C. Intrinsic diffusivities ratios of copper and aluminium at different temperatures and diffusion activation energies in the Cu-Al system are calculated by proposed here methods using literature experimental data. Dislocation pipe and volume diffusion activation energies of pure iron are calculated separately by earlier proposed method using literature experimental data. Aluminium dissolved into NaCl solution as the Al³⁺ ions at room temperature and at temperature 100°C, iron dissolved into NaCl solution as the Fe²⁺ (not Fe³⁺) ions at room temperature and at temperature 100°C, copper dissolved into NaCl solution as the Cu⁺ ions at room temperature and as the Cu⁺ and the Cu²⁺ ions at temperature 100°C. It is found experimentally that copper corrosion is higher than aluminium corrosion, and ratio of electrochemical corrosion rates, k_Cu/k_Al>1, decreases with temperature increasing, although iron electrochemical corrosion rate does not depend on temperature below 100°C. It is obvious, because the melting point of iron is more higher than the melting point of copper or aluminium. It is calculated that the copper electrochemical corrosion rate is approximately equal to aluminium electrochemical corrosion at temperature about 300°C, so copper can dissolve into NaCl solution mostly as the Cu²⁺ ions at temperature about 300°C. The ratio of intrinsic diffusivities, D_Cu/D_Al<1, increases with temperature increasing, and the intrinsic diffusivity of aluminium could be approximately equal to the intrinsic diffusivity of copper at temperature about 460oC. Intrinsic diffusivities ratios in the Cu-Zn system at temperature 400°C and in the Cu-Sn system at temperatures from 190°C to 250°C are analyzed theoretically using literature experimental data. Diffusion activation energies and pre-exponential coefficients for the Cu-Sn system are calculated combining literature experimental results.

Abstract: The vulnerability of Al matrix composites to general and preferential corrosion is due to the intrinsic proneness of binary materials to undergo advanced deterioration. Control of the prevalent sites for evolution and proliferation of confined corrosion strongly influence the corrosion resistance of the composites. The problem for enhanced utilization of composites, has exacerbated with attention on the productive life and resilience to environmental degeneration during operational service. This can be achieved through proper comprehension of the electrochemical mechanism, the intriguing nature of SiC grains and their importance on the secondary phases, metallurgical configuration, and manufacturing process routes. This review confirms the relevance of secondary phases, microstructures and manufacturing processes in relation to SiC particles on the corrosion invulnerability of Al matrix composites to further add corrosion mitigation in design and and technological advancement.

Abstract: Aluminum (Al) - Silicon Carbide (SiC) metal matrix composite is one of the widely used composites in today’s manufacturing industry. Al-SiC composites are produced through several methods such as casting and powder metallurgy, but its production through Reverse Two-Step Sintering (R-TSS) process in powder metallurgy has not been addressed so far. The present work focuses on manufacturing Al-SiC metal matrix composite through reverse two-step sintering process in powder metallurgy. The reinforcement element SiC is embedded with metal matrix element Al in different proportions. Then the consolidated mixture is compacted using the die and punch setup followed by a two-step sintering process suggested by Wong; thereby, the final compact is produced. Further, the processed sample is analyzed for density and hardness tests.