Search Results (199)

Although cemented carbides have been manufactured by the powder metallurgy (P/M) technology for over a century now, systematic developmental efforts are still underway. In the present study, tool life improvements in metal grooving applications are the key objective. Four PVD-coated cemented carbides compositions, dedicated to groove steel, stainless steel, cast iron, and aluminium alloys, have been newly designed, along with their manufacturing conditions. Physical, mechanical and chemical characteristics—such as sintered density, modulus of elasticity, hardness, fracture toughness, WC grain size, and the chemical composition of the substrate material, as well as the chemical composition, microhardness, structure, and thickness of the coatings—have been studied. A series of grooving tests have also been conducted to assess whether modifications to the thus far marketed tool materials, tool geometries, and coatings can improve cutting performance. In order to compare the laboratory and application properties of the investigated materials with currently produced by reputable companies, commercial inserts have also been tested. The experimental results obtained indicate that the newly developed grooving inserts exhibit excellent microstructural characteristics, high hardness, fracture toughness, and wear resistance and that they show slightly longer tool life compared to the commercial ones. Full article

The anodic oxide layer’s porosity is considered a functional feature, acting as a reservoir of lubricants. This feature enables the design of self-lubricating systems that effectively reduce friction and wear. To improve the tribological performance of Al₂O₃ anodic coatings on EN AW 5251 aluminium alloys, this paper presents a modification of the coating with tungsten disulfide (IF-WS₂) nanopowder and its effect on coating resistance. The wear properties of Al₂O₃/IF-WS₂ coatings in contact with a cast iron pin were investigated. The results include the analysis of the friction coefficient in the reciprocating motion without oil lubrication at two loads, the analysis of the wear intensity of the cast iron pin, the characterisation of wear scars, and the analysis of SGP parameters. Two-level factorial analysis showed that load and nanomodification significantly affected the load-bearing parameter Rk. Incorporation of the modifier, especially under higher loads, reduced the Rk value, thus improving the tribological durability of the contact pair. Both load and nanomodification had a notable impact on the coefficient of friction. The use of IF-WS₂-modified coatings reduced the coefficient, and higher loads further enhanced this effect, by approximately 9% at a load of 0.3 MPa and 15% at a load of 0.6 MPa, indicating improved lubricating conditions under greater contact stress. Full article

Aluminium alloy 6082 is widely used in the automotive and aerospace industries due to its high strength-to-weight ratio. However, its structural integrity can sometimes be affected by an early fatigue failure. This study investigates the fatigue performance of extruded 6082-T6 samples through a series of fatigue tests conducted at varying stress levels. The material showed significant variability under identical fatigue conditions, suggesting the presence of microstructural defects. Scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) and scanning transmission electron microscopy (S/TEM) were used to identify the nature and location of the defects and evaluate the underlying mechanisms influencing the fatigue performance. Computer tomography (CT) also confirmed the presence of oxide inclusions on the fracture surface and near the edges of the samples. These oxide inclusions are distributed throughout the material heterogeneously and in the form of broken oxide films, suggesting that they might have originated during the material’s early processing stages. These oxides acted as stress concentrators, initiating microcracks that led to catastrophic and unpredictable early failure, ultimately reducing the fatigue life of micro-oxide-containing samples. These results highlight the need for better casting control and improved post-processing techniques to minimise the effect of oxide presence in the final components, thus enhancing their fatigue life. Full article

The present study examines the structure, properties and use of complex-alloyed hypereutectic aluminium-silicon alloys, emphasising the control of the morphology of primary silicon via treatment with various modifiers as well as their effects on its shape and distribution. Furthermore, this study reviews the experimental work related to the simultaneous modification of primary and eutectic silicon, which leads to the conclusion that favourable results can be obtained by complex modification treatment involving first- and second-type modifiers. After being cast, the AlSi18Cu3CrMn and AlSi18Cu5Mg non-standardised piston alloys are subjected to T6 heat treatment intended to enhance their mechanical performance, harnessing the full potential of the alloying elements. A microstructural analysis of the shape and distribution of both primary and eutectic silicon crystals following heat treatment was employed to determine their microhardness. Full article

This study examines the mechanical and microstructural properties of graphene-reinforced AA2219 composites developed for hydrogen storage tank inner liner applications. A novel processing route combining high-energy ball milling, ultrasonic-assisted stir casting, and squeeze casting was used to achieve homogeneous dispersion of 0.5 wt.% graphene nanoplatelets and minimise agglomeration. The composites were subjected to T6 and T8 ageing treatments to optimize their properties. Microstructural analysis revealed refined grains, uniform Al₂Cu precipitate distribution, and stable graphene retention. Mechanical testing showed that the as-cast composite exhibited a UTS of 308.6 MPa with 13.68% elongation. After T6 treatment, the UTS increased to 353.6 MPa with an elongation of 11.24%. T8 treatment further improved the UTS to 371.5 MPa, with an elongation of 8.54%. Hardness improved by 46%, from 89.6 HV (as-cast) to 131.3 HV (T8). Fractography analysis indicated a shift from brittle to ductile fracture modes after heat treatment. The purpose of this work is to develop lightweight, high-strength composites for hydrogen storage applications. The novelty of this study lies in the integrated processing approach, which ensures uniform graphene dispersion and superior mechanical performance. The results demonstrate the suitability of these composites for advanced aerospace propulsion systems. Full article

One of the most effective methods of improving the properties of aluminium alloys is grain refining using Al-Ti-B master alloys. In contrast, zirconium is a key alloying element, used mainly in 2xxx and 7xxx series aluminium alloys, where it contributes to dispersion enhancement and reduces the rate of dynamic recrystallisation. However, even trace amounts of zirconium—just a few hundredths of ppm—significantly reduce the performance of Al-Ti-B grain refiners, a phenomenon known as ‘Zr poisoning’. This study investigates the impact of holding time and the level of Al-5Ti-1B addition on the microstructure and properties of an AlMgSi(Cu) alloy containing 0.15 wt.% Zr, cast as 7-inch DC billets. The structure and phase distribution were characterised using optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Grain size and morphology were evaluated through macrostructure analysis (etched cross-sections and polarised light microscopy), while chemical and elemental distributions were analysed via SEM-EDS and STEM-EDS mapping. Additionally, Brinell hardness measurements were conducted across the billet diameter to assess the correlation between grain size and mechanical properties. The results show that reducing holding time and increasing the Al-5Ti-1B addition improves grain refinement efficiency despite the presence of Zr. The finest grain structure (150–170 μm) and most homogeneous hardness distribution were achieved when the grain refiner was continuously fed during casting at 80 ppm B. These findings are supported by the literature and contribute to a deeper understanding of the Zr poisoning effect and its mitigation through optimized casting practice. Full article

In addition to ensuring the functionality of objects used in the household, transport or industry at large, applied design focuses on aesthetic qualities related to the external form and condition of a surface. At the same time, there is a trend for plastic, rubber or aluminium objects made by moulding (both injection and casting) to look as if they were made of natural materials. This effect is ensured by properly designed and manufactured surface textures in the mould seats. However, the working surfaces of the moulds often corrode as a result of inadequate maintenance and storage. The aim of this study was to find out how popular agents on the market dedicated to corrosion product removal would change the surface geometrical texture. During the prepared experimental plan, it was also decided to investigate the properties in this respect of one of the popular drinks (i.e., cola) which is sometimes used in workshop practice as an alternative corrosion product removal agent. Based on the results of the study, conclusions were drawn about the short- and long-term effects of the corrosion product removal agents. Full article

Semi-solid processes of aluminium alloys, characterised by the coexistence of solid and liquid phases, offer advantages in terms of mechanical properties and fatigue resistance, thanks to the more globular microstructure. Thermodynamic models can be used to analyse the solidification behaviour and to predict the solidification window, ΔT. The CALPHAD method enables the calculation of the phases formed during solidification and the optimisation of alloy composition to meet specific industrial requirements. This study aims to assess how thermodynamic properties in both liquid and solid phases affect the ΔT. Initially, the influence of thermodynamic properties of pure components and interaction parameters was analysed in simplified regular binary systems. To compare these findings with real industrial systems, Al-based alloys were examined. Using available databases, the ΔT was estimated via the CALPHAD method adding alloying elements commonly found in secondary Al-alloys. Finally, the same minority alloying elements were added to Al-Si 8 and 11 wt.% alloys, and the corresponding ΔT were calculated. Cr, Fe, Mg, Mn, and Ti increase the ΔT, while Cu, Ni, and Zn decrease it. The obtained results may serve as a valuable tool for interpreting phenomenological observations and understanding the role of minority elements in the semi-solid processing of secondary Al-Si casting alloys. Full article

The characterisation of aluminium casting alloys with iron concentrations exceeding current standards is essential, as upcycling has recently become a significant concern in achieving a more circular economy. Secondary aluminium casting alloys often exhibit insufficient mechanical properties for load-bearing automotive applications due to contamination with iron, mainly due to alloy mixing or remnants from end-of-life products during downcycling. This trend is anticipated to soon lead to a surplus of scrap. This study aims to fully understand the microstructural changes, intermetallic phase morphologies, and defect formation in AlSiMg alloy highly contaminated with Fe that exists in Al scraps and is detrimental for upcycling purposes. The investigation examined the AlSi7Mg0.3 alloy with Fe concentrations ranging from 0.1 to 3.8 wt.% Fe, employing thermodynamic simulations, hardness testing, quantitative image analysis, and corrosion tests. Among these alloys, the AlSi7Mg0.3-3.8Fe, containing the highest level of contamination, exhibited the most complex microstructure. This microstructure is characterised by the presence of two distinct Fe-rich intermetallic phases with diverse shapes and sizes: petal-like α′-Al₈Fe₂Si, long and thick β-Al_4.5FeSi plaques, and very thin β-Al_4.5FeSi needles. The significant growth in these phases with higher Fe concentration resulted in increases in hardness (15 HBW), porosity (1.39%), and corrosion rate (approximately 12 times). Full article

In this study, the ProCast software (version 2014) incorporating the CAFE model is applied to conduct numerical simulation analysis of the directional solidification process of titanium–aluminium alloy cylindrical rods at varying withdraw rates. According to the analytical results, the withdraw rate is a critical parameter that affects the morphology of the solid–liquid interface and the grain growth behavior during the directional solidification process. An increase in the drawing rate facilitates nucleation undercooling within the rod, inducing a shift in grain morphology from columnar to equiaxed. At a drawing rate of 1 mm/min, the solid–liquid interface exhibits the most stable morphology, as characterized by a flat interface. As indicated by further analysis, at this drawing rate, specific grain orientations are eliminated during competitive growth with an increase in solid fraction, culminating in the formation of columnar grain structures. Additionally, the impact of drawing rate on grain size and number is investigated, with an increase observed in grain number with drawing rate and a decrease found in grain size. The findings of this study contribute to a deeper understanding of mechanisms behind the grain morphology evolution of titanium aluminide, providing crucial theoretical support for optimizing directional solidification processes. Full article

The expansion, cracking and deterioration of properties during utilisation and solidification of municipal solid waste incineration bottom ash are key problems that are caused by the reaction of metallic aluminium in the bottom ash in the highly alkaline environment of hardened Portland cement. In this study, polyaluminium sulphate (PAS) was introduced into ordinary Portland cement (OPC) to inhibit the corrosion of aluminium alloy. The results indicate that PAS successfully inhibited the corrosion of Al in hardened OPC paste, prevented the expansion and cracking, reduced the amount of hydrogen gas release and formed a thinner and dense corrosion layer on the Al plate surface. The mechanism of corrosion inhibition of Al by PAS was the increase of initial Al(OH)₄⁻ concentration by hydrolysis, which expanded the pH range of passivation and transformed the porous loose bayerite layer to a dense homogeneous one around the Al plate without modification of the corrosion product (bayerite). The corrosion rate of the Al alloy in hardened OPC paste was reduced by 213 times by the addition of PAS, from 288.30 mm a⁻¹ without PAS addition to 1.35 mm a⁻¹ with PAS addition. This study casts light on the effective inhibition of corrosion of the Al alloy in OPC. Full article

Aluminium thin wall castings are gaining wide acceptance in the automotive industry because of their incomparable design flexibility and higher mechanical properties. For these thin wall castings, fluidity plays a vital role in determining the quality of the final product. The aim of this work is to provide a detailed insight into the development of a multi-channel testing methodology to evaluate the fluidity of aluminium foundry alloys for thin wall applications. AlSi10MnMg foundry alloy has been used to conduct a series of experiments with the aim of designing operative protocols that achieve higher repeatability of the results. The fluidity of the investigated alloy was observed in channels of various cross-sections at three different pouring temperatures, i.e., 680, 710, and 740 °C. The obtained results show that experiments conducted following closely the designed operative protocols, result in achieving higher repeatability. It was also observed that by increasing the pouring temperature, the fluidity and repeatability of the alloy increased greatly. The 3D transient simulations were conducted by means of Altair^® Inspire™ Cast 2021.2 software to study the molten metal behaviour, i.e., solidification temperature and time at the end of each strip for the studied pouring temperatures. The results further reveal that the design methodology, if executed with intrinsic accuracy and precision, will provide a reliable pathway to determine the fluidity of aluminium alloys for various industrial applications. Full article

The rapidly growing field of metal additive manufacturing (AM) has enabled the fabrication of near-net-shape components with complex 3D structures in a more reliable, productive, and sustainable way compared to any other manufacturing process. The productivity of AM could be significantly increased combining conventional and AM technologies. However, the application at an industrial level requires the validation of the AM process itself and the assurance of the soundness of the junction between the substrate and the deposited metal at a sufficiently rapid metal deposition rate. In this work, the validation of additively manufactured samples of Al-5356 alloy was performed. These were manufactured partially via an ablation casting process and partially via laser metal deposition using a metallic wire (LMwD). The deposited material showed low porosity levels, i.e., below 0.04%, and a small number of lack-of-union defects, which are detrimental to the mechanical properties. In the tensile samples centred at the junction between the ablated and deposited materials, it was found that when the AM part of the sample exhibited no lack-of-union defects, the region manufactured using LMwD showed higher strength than the ablation-cast part. These results suggest that the combination of ablation casting and LMwD is a competitive technique for the manufacturing of Al-5356 alloy parts with complex geometries. Full article

This study aims to enhance the electrical conductivity of commercially pure aluminium by minimizing impurities and grain boundaries in its microstructure, ultimately improving the efficiency of electric motors constructed from rotors with squirrel cages made from this material. For this purpose, an aluminium–boron (AlB8) master alloy was added to aluminium with a purity of 99.7%, followed by the application of a grain-coarsening heat treatment to the rotors. To obtain commercially pure aluminium with boron additions of 0.05% and 0.1% by weight, specific amounts of the AlB8 master alloy were added into aluminium with a purity of 99.7%. Using these materials, squirrel cage components of rotors were produced via the high-pressure die-casting method. Subsequently, a grain-coarsening heat treatment of the rotors was performed at temperatures of 450 °C, 500 °C, and 550 °C, with holding times of 2, 6, and 10 h. The Box–Behnken design, which is based on statistical experimental design and response surface methodology, was employed to investigate the effects of adding boron and varying the heat treatment temperature and holding time on the electrical conductivity of commercially pure aluminium. The results showed that the synergistic effect of adding boron at 0.05 wt.% and applying the grain-coarsening heat treatment at a temperature of 550 °C for a holding time of 10 h significantly enhanced the electrical conductivity of commercially pure aluminium, increasing it from 60.62% IACS to 63.1% IACS. Correspondingly, the efficiency of the electric motor increased from 90.35% to 91.53%. These findings suggest that this hybrid method not only enhances the electrical conductivity of commercially pure aluminium but also has strong potential to improve its other properties, such as thermal conductivity. This will lead to products composed of components manufactured from the materials exhibiting better performance characteristics, such as increased efficiency and extended service life. Consequently, this innovative method will contribute economically and environmentally by facilitating the manufacture of high-performance products. Full article

Polybenzoxazine (PBz) resins exhibit excellent mechanical, thermal, and adhesive properties, making them interesting candidates for coating applications. Moreover, thanks to the incorporation of exchangeable ester bonds within the PBz network, the coating presents healable properties that are catalyzed by the intrinsic presence of tertiary amine within the PBz backbone. Unfortunately, these tertiary amine functions are also responsible for the limited resistance of such systems to acid environments by protonation. To address this limitation, the protection of tertiary amines inherent to the PBz network was investigated in this study by incorporating an aromatic group close to the amine function to minimize its protonation via hindrance/mesomeric effects. More precisely, benzoxazine precursors based on monoethanolamine (mea) and aminophenylethyl alcohol (Apa) were synthesized and tested as protective coatings of aluminium alloy substrates (AA1050). The resins were characterized by NMR, FTIR, rheology, TGA, DSC, and DMA. PBz synthesized from Apa exhibits enhanced thermal stability, reduced swelling rates in both water and acid, and shortened relaxation times. After application via solvent casting on AA1050 substrates, the acid resistance of the coatings was evaluated. Electrochemical impedance spectroscopy results demonstrated better resistance of the Apa-based resins in 0.1 M sulfuric acid after one month of immersion. Full article