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| 2. |
- Awe, Samuel A., et al.
(author)
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Development of new Al-Cu-Si alloys for high temperature performance
- 2017
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In: Advanced Materials Letters. - : VBRI Press. - 0976-3961 .- 0976-397X. ; 8:6, s. 695-701
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Journal article (peer-reviewed)abstract
- In a quest to develop new light metal alloys that can perform excellently at elevated-temperatures (from 300°C to 400°C), a ternary eutectic Al-Cu-Si alloy was exploited to gain a deeper understanding of the alloy system and its suitability for high temperature applications. The alloys studied, with chemical composition of Al-27%Cu-5%Si (by weight percent) with Ni addition in the range of 0 to 1.5%wt, were cast in a rapid solidification casting technique. The solidification characteristics of the alloy was studied using the Thermo-Calc software. Microstructures were characterized in a scanning electron microscope coupled with energy dispersive spectrometry (SEM-EDS). Finally, the elevated-temperatures tensile properties of the alloys were investigated. Comparing the microstructures and mechanical properties of these Al-Cu-Si(-Ni) alloys with conventional Al-Si alloy A319, the refined microstructure with dispersed Ni intermetallic particles formed in the as-cast Al-Cu-Si(-Ni) alloys deliver improved elevated temperature properties. In particular, the yield strength and ultimate tensile strength of the new alloy with 1.5% Ni at 400?C were observed to be 220% and 309% higher, respectively, than for conventional A319 alloy.
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| 3. |
- Lattanzi, Lucia, et al.
(author)
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On the possibility of using secondary alloys in the production of aluminum-based metal matrix composite
- 2024
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In: Crystals. - : MDPI. - 2073-4352. ; 14:4
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Journal article (peer-reviewed)abstract
- Aluminum-based composites provide tribological performance and thermophysical properties that, combined with being lightweight, are suitable for their application in automotive brake discs. Aluminum alloys allow the use of secondary materials to produce composites, with the drawback of several elements, impurities, and oxides that can harm the mechanical and thermophysical properties. This preliminary study explored the mechanical and thermophysical performance of a composite material produced with a secondary matrix alloy. Overall, the results are promising, with a minimal decrease in mechanical and thermophysical properties despite clustered silicon carbide particles in the composite with the secondary matrix. The challenges in effectively dispersing carbides in the melt seem linked to aluminum oxides, and future microstructural investigations will aim to clarify this aspect.
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| 4. |
- Lattanzi, Lucia, et al.
(author)
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The effect of Ni and Zr additions on hardness, elastic modulus and wear performance of Al-SiCp composite
- 2022
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In: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 169
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Journal article (peer-reviewed)abstract
- The strive for lightweight in the automotive industry points to aluminium metal matrix composites as substitutes of cast iron in brake discs. The wear performance of the material is critical, besides suitable mechanical resistance and thermal properties. The present study investigated the wear behaviour of Al-Si alloys reinforced with silicon carbide particles. The matrix alloy was added with nickel and zirconium, and nanoindentation was performed to determine intermetallic phases' hardness and elastic modulus. The addition of 20 wt% carbides determined an elastic modulus 35–40 % higher than the matrix alloys. Wear rate was in the 2–8 * 10-5 mm3/N * m range for all materials. The tribo-layer had a critical role in the wear performance, as the coefficient of friction decreased during wear.
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| 5. |
- Lattanzi, Lucia, et al.
(author)
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The influence of Ni and Zr additions on the hot compression properties of Al-SiCp composites
- 2022
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In: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 905
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Journal article (peer-reviewed)abstract
- The present work investigates different additions of nickel and zirconium to the matrix alloy of Al-SiC metal matrix composites to enhance their high-temperature performance. These composites are promising for the demand for lightweight solutions for automotive components like brake discs. In such components, the compression behaviour at elevated temperatures is crucial. The resulting properties were combined with microstructural analysis. Ni additions led to a continuous improvement of the mechanical response, but the same result did not hold for the Zr additions. The interaction of SiC particles, eutectic silicon, and eutectic Ni-based phases led to a 44 % increment of the activation energy.
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| 6. |
- Mahade, Satyapal, 1987-, et al.
(author)
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Sliding wear behavior of a sustainable Fe-based coating and its damage mechanisms
- 2022
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In: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 500-501
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Journal article (peer-reviewed)abstract
- The current industry demand is to identify suitable alternatives to the risk-of-supply prone and/or toxic, WC-Co and electrolytic hard chrome coatings without comprising the desired wear performance. Therefore, compositions based on abundantly available elements (e.g. ‘Fe’) that possess adequate wear resistance are desirable from health, sustainability and economic standpoints. In this work, crystalline Fe-based (Rockit-401) coatings were processed using two different thermal spray routes, i.e. HVOF and HVAF spraying. The influence of deposition route and processing conditions on the microstructure, porosity content, hardness and phase composition was examined. The as-deposited coatings were subjected to mild (5 N) and harsh (15 N) dry sliding wear test conditions by employing alumina ball as the counter surface material, and their wear performance was examined. Mild sliding wear test conditions (5 N) resulted in anomalous wear behavior, where the abrupt drop in CoF at several instances during the test was observed in all the investigated coatings. On the other hand, under harsh wear test conditions (15 N), such an abrupt dip in CoF was not observed. Detailed wear mechanisms of the coatings were revealed under different test conditions (5 N and 15 N). This work sheds light on processing, wear behavior and wear mechanisms of a sustainable and high-performance coating that fulfills non-toxic and sustainability goals in tandem for tribological applications. © 2022 The Authors
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| 7. |
- Wikedzi, Alphonce, et al.
(author)
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Recovery of antimony compounds from alkaline sulphide leachates
- 2016
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In: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 152, s. 26-35
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Journal article (peer-reviewed)abstract
- In copper metallurgy, antimony impurities usually form alloys and compounds with the transition metals to make up the basic building blocks of a speiss phase. This speiss phase is generally rich in copper and precious metals, which are desirable to recycle and recover at the smelter. The presence of this impurity unfortunately creates a build-up of this metal in the copper circuit, leading to problems during copper refining processes. Therefore, a removal or reduction of the antimony impurity to an acceptable level is a necessary step before the speiss can be recycled at the smelter for the recovery of its valuable metals. A lead silicate slag that was obtained after smelting a copper speiss admixed with silica, soda and lead oxide, was leached in alkaline sulphide solution to selectively dissolve its antimony content. Furthermore, the pregnant sulphide leachate was purified by precipitation and crystallization techniques to recover antimony as sodium thioantimonate and sodium hydroxyl antimonate using synthetic Na2S-NaOH-Sb2S3 solutions. The leaching results indicate that the highest amount of antimony and arsenic extracted from the material after 24 h at 100 °C and reagent concentration of 30 g/L NaOH + 30 g/L S2− was 83% and 90%, respectively. In the precipitation process, the addition of hydrogen peroxide to the alkaline sulphide leachate prompts the precipitation of antimony as NaSb(OH)6. The result also implies that b100% of stoichiometric hydrogen peroxide is required to completely oxidize the total amounts of both Sb3+ and S2− in the solution and to quantitatively precipitate N90% of the antimony in solution. The influence of catalytic agents and temperature on the process was not clearly reflected in this investigation due to the exothermic reaction with hydrogen peroxide. Moreover, the addition of elemental sulphur to the sulphide leachate also in- fluences the precipitation of antimony as sodium thioantimonate.
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| 8. |
- Wikedzi, Alphonce, et al.
(author)
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Selective Extraction of Antimony and Arsenic from Decopperization Slime Using Experimental Design
- 2017
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In: Journal of sustainable metallurgy. - : Springer. - 2199-3823 .- 2199-3831. ; 3:2, s. 362-374
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Journal article (peer-reviewed)abstract
- The aim of the present study is to selectively extract antimony and arsenic from decopperization slime through alkaline sulfide hydrometallurgy with a view to recycle the obtained solid residue within the copper smelter, and also regenerate the sulfide lixiviant during the process. Rechtschaffner experimental design was used to evaluate the joint influence of several experimental parameters such as leaching temperature, Na2S concentration, solid concentration, and reaction time on the extraction of antimony and arsenic from the material. The most active parameters influencing the extraction of the metals are solid concentration and reaction period. In addition, the results show that solid concentration interacted strongly with the leaching time and slightly with reaction temperature, which is an indication that solid concentration is the predominant influencing factor in removing antimony and arsenic from the material. It is also indicated from the results that about 95% Sb and 89% As were extracted when 50 g/L of the decopperization slime was dissolved in alkaline sulfide lixiviant containing 200 g/ L Na2S ? 20 g/L NaOH at 60 C for 24 h. Moreover, analysis of the leach residue reveals that copper sulfide and lead sulfide remain as the main constituents of the residue. The bismuth-containing mineral phase was not observed in the residue because of its low concentration, and also the Sb/As-bearing mineral phases were not detected due to the selectivity of the leaching reagent to the metals. Based on the experimental results from this investigation, a process flowsheet for the alkaline sulfide treatment of a decopperization slime was proposed with a view to eliminating its antimony and arsenic contents in a sustainable manner.
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