Multiscale analysis of crystalline defect formation in rapid solidification of pure aluminium and aluminium–copper alloys

Rapid solidification leads to unique microstructural features, where a less studied topic is the formation of various crystalline defects, including high dislocation densities, as well as gradients and splitting of the crystalline orientation. As these defects critically affect the material’s mechanical properties and performance features, it is important to understand the defect formation mechanisms, and how they depend on the solidification conditions and alloying. To illuminate the formation mechanisms of the rapid solidification induced crystalline defects, we conduct a multiscale modelling analysis consisting of bond-order potential-based molecular dynamics (MD), phase field crystal-based amplitude expansion simulations, and sequentially coupled phase field–crystal plasticity simulations. The resulting dislocation densities are quantified and compared to past experiments. The atomistic approaches (MD, PFC) can be used to calibrate continuum level crystal plasticity models, and the framework adds mechanistic insights arising from the multiscale analysis. This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.

Production and Characterization of Commercial Aluminum Powders by a New Nozzle Design and Atomization Unit

A large area cross section of the production of spherical metal powders by gas atomization in the manufacturing method. Powder metal characteristic improves with small powder size. This aim was realized by vertical gas atomization unit, a new a closely-matched nozzle system and manufacture. In the experimental studies, pure aluminium powders which has an important place in the automotive, air and defence industries were produced. In the studies carried out with the Vertical Gas Atomization unit, aluminium was superheated up to 900°C and atomized at different gas pressures (20-30 bar). Scanning electron microscope (SEM) and particle size measuring device were used for the characterization and size measurements of the produced powders, respectively. The average particle size of the finest powder produced with increasing atomization pressure was determined as d50=19.50µm. Aluminium powder shape and morphology was used as spherical and very little satellization was seen. Keywords: Powder Metallurgy, Atomisation, Nozzle, Al powder, Characterisation

Sustainable Silicon and High Purity Alumina Production from Secondary Silicon and Aluminium Raw Materials through the Innovative SisAl Technology

Calcium aluminate slag produced by the aluminothermic reduction of silica is tested as a candidate raw material for the hydrometallurgical production of pure aluminium chloride hexahydrate (ACH) through leaching with hydrochloric acid. The crystallization of ACH follows by sparging the pregnant liquor with hydrochloric gas. Almost total extraction of Al is achieved with the use of azeotropic HCl acid solution (5.9 M) at 80 °C and 1 h retention time. A pregnant liquor with approximately 20 wt% AlCl3 is produced as a base for ACH crystallization by sparging it with gaseous HCl. The ACH produced is re-dissolved and crystallized three to four times until high purity is achieved. High purity ACH acts as a precursor for producing High Purity Alumina (HPA), a high added value material used in LEDs and lithium-ion batteries and other niche applications.

Microstructure and Properties of the Aluminum Alloyed with ZrO Powder Using Fiber Laser

The scope of the work covers the development of the relationship between the chemical composition of surface-modified aluminium and its mechanical properties. This article presents the impact of laser alloying with ZrO powder on the microstructure and mechanical properties of pure aluminium. In order to study the phenomena occurring during the laser alloying process, microstructural studies were carried out using optical microscopy. Additionally, the properties of the obtained alloy were tested - abrasion resistance and hardness measured at low load force. As a result of the alloying process, three distinct zones were identified: the remelting zone (RZ), the diffusion zone (DZ) and the heat affected zone (HAZ). The surface modification resulting from laser alloying increases the hardness and abrasion resistance of the material.

Condensation performance of superhydrophobic aluminium surface material used for cooled ceiling panels under highly humid indoor conditions

The application of radiant cooling systems is very limited in hot and humid areas due to condensation. Research on superhydrophobic surface (SHS) materials has shown the potential of restricting the size of condensate drops on these materials, which provides possibilities for preventing dripping and thereby alleviating condensation risks for cooled ceiling panels, but there are few studies on the anti-condensation performance of these materials under the scale and conditions of building applications. An experimental study of condensation on superhydrophobic materials under indoor conditions is presented in this article. Two material samples with a size of 2.5 cm, including a superhydrophobic aluminum sheet and a pure aluminium sheet, were affixed on a cooled ceiling panel to perform the experiment under the following condition: temperature is 25°C ± 0.5°C, relative humidity is 80% ± 5%, and air dew point is 21.4°C. The panel was cooled by chilled water of 6°C for eight hours. The measured temperature on sample surfaces was about 13.5°C during the experiment. After eight-hour condensation, the diameter of drops on the superhydrophobic aluminum sheet was less than 150 μm, while the max drop on the pure aluminum sheet was near 4 mm. The results suggested that the size of condensate drops on superhydrophobic surface materials can be largely restricted during a long-time indoor operation below the dew point, which shows their potential for constructing condensation-free radiant cooling panels.

Plasmonic Properties of Al2O3 Nanoshell with a Metallic Core

Background: Al is the promising candidate for the deep UV and longer wavelength range plasmonic applications. But it is difficult to have the pure Aluminium nanostructure as it is easily oxidized forming a thin layer of Al2O3. In this paper we have evaluated the field enhancement of oxide layer on metallic shell (Al-Al2O3 and Au- Al2O3) for single and dimer core-shell configuration and shown potential of oxide layer in SERS. Methods: The Finite Difference Time Domain (FDTD) has been used to evaluated the LSPR and field enhancement of single and dimer Al-Al2O3 and Au- Al2O3 nanostructure. Results: The results exhibit the tunable plasmon resonance on varying the inner and outer radii of the Al2O3 shell. A redshift and decrease in enhancement were observed as shell thickness increases whereas on increasing the core size the enhancement gets increased in the case of Au-Al2O3 and gets a decrease in Al-Al2O3 due to quadrupole contribution. But on comparing the Au-Al2O3 with Al-Al2O3 for the same particle size, Al-Al2O3 shows larger enhancement because Au has to compete with its inter band transition. Conclusion: By optimizing the thickness of the shell and core size, it can be concluded that an ultrathin shell of Al2O3 can give higher enhancement. With Al as a core metal the enhancement increases as compared to Au-Al2O3. Since a single Al-Al2O3 nanoshell has shown a huge enhancement we have considered the multimer configuration of two identical nanoshell. Due to coupling between two nanoshell a huge increase in enhancement factor ~1012 was observed for Al-Al2O3 dimer nanoshell in the UV region.

Studies on Wear Behaviour of Coated RHA-TIO2-LM24 Aluminium Alloy Composite

Liquid metallurgy method based aluminium matrix composites (AMCs) are extensively utilized in diverse engineering applications including shipbuilding, structural, non-structural, automotive, and aerospace owing to their superior strength, weightless, low density, excellent corrosion, and wear resistance. In the present research work, liquid state technique is employed to prepare the LM4/RHA/TiO2 composites containing four different mass proportion of RHA and TiO2. The weight proportion of reinforcements ie RHA-1,3&5 and TiO2 2,5&6 respectively.From the dry sliding wear studies, it is evident that the incorporation of RHA and TiO2 particles into the LM24 aluminium matrix alloy increases the wear resistance properties up to 45% as compared with the dry sliding behaviour of pure aluminium LM4 alloy. Dry sliding wear results revealed that the parameters like varying weight percentage, sliding speed, and applied load are the direct impact on the wear behaviour of the hybrid composites. A reduction of up to 34 % wear rate was observed by incorporation of 5% of RHA and 1% & 6 %of TiO2 particles as compared with the remaining percentage of reinforcements. The developed Coated RHA-TIO2 -LM24 aluminum alloy composite exhibits excellent mechanical properties, can be used in long-term applications in which saving weight is an important feature, such applications include and automotive engine parts and aerospace industry. In automotive industry, it can be used for making Brake disc, Turbo-compressors, Pump supporting parts, rear axle, differential housing.