Department of Chemical, Metallurgical and Materials Engineering -Research Articles

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https://hdl.handle.net/20.500.14519/71

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3D finite element analysis and experimental correlations of laser synthesized AlCrNiTiNb high entropy alloy coating.
(Elsevier, 2023-11-23) Kanyane, L.R.; Lepele, P.; Malatji, N.; Shongwe, M.B.
A 3D Finite Element Analysis (FEA) model of laser cladding process of AlCrNiTiNb high entropy alloy (HEA) coatings on Titanium alloy (Ti6Al4V) substrate has been developed taking into account heat transfer and free surface movement. The use of Ti6Al4V is highly evident in applications such as aerospace, automobile and marine environments due to their outstanding specific strength to weight ratio. Although they have high strength useful for fabrication of engineering components and movable parts in a mechanical system, Ti6Al4V are restricted to non-friction applications as a result of their low hardness. In this work, AlCrNiTiNb HEA hard coating with equi-atomic ratio was synthesized on Ti6Al4V alloy substrate by laser cladding technique to mitigate the limitations. Prior to experimental method, a 3D computational model was developed to simulate the physical phenomena based on heat transfers involved during laser surface cladding (LSC) of HEA coating on Ti6Al-4V alloy by a laser-assisted direct energy deposition technique. COMSOL Multiphysics 5.3a was used to create a model using heat transfer in solids module incorporating temperature distribution during the layer-wise build-up of 3 layers. The experimental validation showed that the microstructural analysis by scanning electron microscope (SEM) resulted in coating having dendritic and interdendritic structure which resulted in good metallurgical bonding. X-ray diffraction (XRD) analysis displayed that AlCrNiTiNb alloy coating is composed of ordered and disordered solid solution phases (BCC and FCC) with no intermetallic compounds formed. Energy dispersive spectrometer (EDS) confirmed the presence of elements used. The microhardness of AlCrNiTiNb HEA coating reached maximum value around 892 HV which is more than of the substrate. The microhardness increased significantly due to the combination of BCC and FCC solid solution phases.
Electrochemical and Tribological performance of Ti–Al with xNb addition synthesized via laser In situ alloying.
(Springer Nature Switzerland AG, 2023-11-30) Kanyane, L. R.; Raji, S. A.; Tlotleng, M.
Additive manufacturing is a growing technique of producing 3D parts directly using metal powders or wires melted with a high-powered intensity beam or laser. It is still a challenging process as to how laser processing parameters such as gas flow rate and powder flow rate can profitably be adopted to significantly produce Ti–Al-based materials from elemental powders to synthesize alloys that are defect-free and have good mechanical properties. The density of titanium aluminide (Ti–Al) intermetallic alloys makes it gain lots of interests due to its potential ability to substitute nickel-based superalloys in gas turbine engines. This work aims to investigate the effects of Niobium (Nb) additions on Ti–Al–xNb ternary alloys created via the use of 3D printing technology, specifically looking at microstructural evolution, microhardness, electrochemical behavior, and tribological properties. Ti–Al–Nb alloy was synthesized at scan speed of 26 in/min and laser power of 450 W. The structural morphology of the alloys produced was investigated using scanning electron microscopy equipped with energy dispersive spectroscopy and the electrochemical studies of the in situ alloyed Ti–Al–xNb were studied using potentiodynamic techniques. Using an Emco microhardness tester, the microhardness characteristics of the produced TiAl–xNb alloys were examined. From the results obtained, it was observed that the microstructure showed not much substantial cracking or crack initiation. The micrographs are evident of refined microstructure associated to increase in Nb feed rate with α-Ti3Al, γ-TiAl and precipitates of β-TiAl phases as the distinctively identified in the microstructure. The highest recorded microhardness value of 679.1 HV0.5 was achieved at Nb feed of 0.5 rpm and gas carrier of 2 L/min. The fabricated Ti–Al–Nb alloys showed good corrosion resistance behavior in HCl and appreciable wear characteristics with coefficient of friction of 0.412, 0.401, and 0.414 µ at B1, B3, and B5, respectively.
Experimental and computational thermal analysis of Ti-based alloy produced by laser metal deposition technique.
(Springer and Minerals, Metals and Materials Society (TMS), 2024-02-02) Kanyane, Rudolf L.; Malatji, Nicholus; Poopola, Patricia A.; Raji, Abiola S.; Pityana, Sisa; Shongwe, Brendon M.; Tlotleng, Monnamme
A Ti-Fe-Si-Cr-Nb alloy was fabricated using laser metal deposition (LMD) technique. The laser power and scanning speed were varied during fabrication to optimize the processing parameters. The thermal behavior during LMD processing was modeled and simulated by means of COMSOL Multiphysics 6.0 software. The samples produced were characterized using an optical microscope, X-ray diffractometer, and scanning electron microscope coupled with energy dispersive spectroscopy. The microhardness and wear behavior of the alloy were tested using a diamond indenter and ball-on-disk wear machine. The results obtained showed that the alloys exhibited similar dendritic microstructure for all processing parameters. The formation of cracks and pores were evident mainly in samples that were produced at high scanning speed and low laser power. A decrease in microhardness was noticed when the laser power was increased, while an increase in scanning speed yielded samples with high microhardness values. The alloy showed good tribological behavior, but no clear relationship between the wear resistance of the alloy and the variation of the laser processing parameters could be established.
Synthesis, corrosion and structural characterization of kenaf nanocellulose on Zn-ZnO-xCn electrolytic coatings of mild steel for advanced applications.
(Elsevier Ltd., 2020-06-09) Anyanwu, B.U.; Oluwole, O.O.; Fayomi, O.S.I; Olorunnisola, A.O.; Popoola, A.P.I.; Kuye, S.I.
Combating the menace of corrosion attack in pipeline is a significant source of expenditure for most oil and gas industries. Mild steel is the most utilized steel employed in producing oil pipelines as a result of their availability, machinability, and cost. This research aimed to develop ternary zinc-zinc oxide-nanocellulose (Zn-ZnO-Cn) coatings on mild steel substrates for improved structural and corrosion resistance in acidic media by electrodeposition method. Potentiodynamic polarization was used to determine the corrosion resistance properties of the coating. The surface morphologies were determined by scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffractometer. The results showed that all the developed composite coatings recorded lower corrosion rate values than that of the substrate (mild steel) sample, whose value was 5.3243 mm/yr. Sample C8 (Zn-20gZnO-20gCn) had the lowest corrosion rate value of 0.1682 mm/yr and this corresponded to a coating protection efficiency of 96% on the substrate. Also, sample B1 (Zn-20gZnO-0gCn), among the developed coatings, gave the highest corrosion rate value of 1.8435 mm/yr with a protection efficiency of 66%. The combined properties of the coating materials were able to form protective barriers on the substrate in the corrosive media.
Environmental sustainability of municipal wastewater treatment through struvite 2 precipitation: Influence of operational parameters.
(Elsevier Ltd., 2020-10-26) Mavhungu, A.; Foteinis, S.; Mbaya, R.; Masindi, V.; Kortidis, I.; Mpenyana-Monyatsi, L.; Chatzisymeon, E.
The environmental sustainability of wastewater treatment through phosphate (P) and ammonia (N) chemical precipitation (struvite) was examined using the life cycle assessment methodology. Thermally activated (calcined) cryptocrystalline magnesite was used towards struvite formation and four process parameters (contact time, magnesite dosage, initial wastewater pH and temperature) were studied. Raising wastewater’s temperature to promote ammonia stripping was found to be environmentally unsound. Magnesite dosage and contact time were identified as environmental hotspots, but not pH. In terms of environmental relevance, when using ReCiPe 2016 life cycle impact assessment method the human health damage category was mostly affected, followed by resource availability, while ecosystems category was affected to a much lesser extent. Environmental impacts were grossly attributed to South Africa’s fossil fuel-dependent energy mix, suggesting that renewable energy could largely improve the system’s environmental performance. The optimal conditions, from the environmental perspective, were found to be 0.2 g L-1 feed dosage and 10 min mixing, at ambient temperature and pH (total environmental footprint 60.9 μPt per treated L of wastewater). To improve N removal efficacy, which is desirable in real-world applications, higher feed dosages and mixing durations are required, albeit at the expense of environmental sustainability (e.g. the 180 min and 16 g L-1 dosage environmental footprint sharply rises to 1.87 mPt L-1. The net impact approach revealed that the avoided environmental impacts on the midpoint impact categories freshwater and marine eutrophication grossly outweigh the corresponding environmental impacts of the treatment process. Results suggest that when using a low contact time and magnesite dosage, struvite precipitation could act as a fast, efficient, and environmentally friendly pre-treatment step to practically remove P and grossly reduce N from wastewater. On the other hand, with higher feed dosages and mixing durations struvite precipitation could act as a promising secondary wastewater treatment method with an overall low environmental footprint. Overall, results complement the existing body of knowledge on the techno-economic performance of such systems and provide insight to decision- and policymakers to sustainably scale the process, at village- or industrial-level, in rural South Africa, Lesotho, and further afield.
Electrolytic deposition of super-smart composite coating of Zn-V2O5- NbO2 on low carbon steel for defence application.
(Elsevier Ltd., 2018-07-09) Fayomi, O.S.I.; Kanyane, L.R.; Popoola, A.P.I.; Oyedepo, S.O.
Despite the massive usages of low carbon steel in automobile for engineering components, its corrosion and high friction coefficient in aggressive environment make it limited in service. This paper is aimed at modifying low carbon steel structural component with thin film composite for enhanced mechanical and corrosion properties. The steel structure was electrodeposited with Zn-V2O5 and embedded with varied NbO2 weight concentration of 6e12 wt % based electrolyte. Scanning electron microscope (SEM) and high optical microscope was used to study the microstructural evolution of the fabricated coatings. The thermal stability of the fabricated coatings was studied in an isothermal furnace at 300 C and 600 C and further characterized using a high-tech optical microscope. Potentiodynamic polarization technique was used to investigate the corrosion behavior of the composites in 3.65% NaCl. From the result, the effect of NbO2 on Zn-V2O5-NbO2 was massive with improved crystal grain within the coatings lattices. The coating possesses strong metallurgical bonding and good corrosion resistance properties of about 0.315 mm/yr corrosion rate compare to 4.1 mm/yr of as-received sample. No doubt the impact of thermal shock on the resilient characteristics of the composite coating was moderate owing to the stable adherent properties of the deposited coatings.
Data on the influence of ECA implant on microhardness and wear characteristics of composite coating on mild steel.
(Elsevier Inc., 2018-11-12) Fayomi, O.S.I.; Kanyane, L.Rudolf.; Popoola, A.P.I.
In this study, the effect of the incorporation of composite and eco-friendly particles to develop new engineering materials on the developed zinc electrolyte containing TiO2/TiB and Solanum tuberosum is presented. The electro-depositions were completed at 20 min at a stirring rate of 150 rpm at temperature of 50 °C and pH of 4. The effect of S. tuberosum (ST) as bath additive at varied interval of 5–25 ml to the coating properties was noted. Electrodeposition parameters were constant at a voltage of 3.5 V for Zn-based coatings. The outline of bath condition as it influences the microhardness and wear rate were set into consideration. Hence, the coating microhardness and wear rate at constant electrodeposition parameters and varied ST were acquired. Hence, liquid fluid additives can be used for performance of fabricated coatings in advanced surface engineering application.
Synthesis and characterization of al–siC composite coatings on 316L stainless steel fabricated via laser cladding technique.
(Springer, 2021-08-26) Kanyane, L.R.; Malepe, T.J.; Malatji, N.; Popoola, A.P.I.
Al–SiC composite coatings were successfully fabricated on 316L stainless steel substrate using laser cladding technique. The microstructure of the coatings was characterized by Scanning electron microscope (SEM) together with energy-dispersive spectrometer (EDS), while the phases that formed were identified using x-ray diffractometer (XRD) equipment. The microhardness properties of the cladded samples were measured using Vickers hardness tester machine. Electrochemical behavior of the fabricated alloy was analyzed using Autolab potentiostat equipped with nova software. The results revealed that the coatings exhibited a dendritic microstructure with SiC particles segregated along the grain boundaries. Refinement of the microstructure was achieved at high laser scan speeds and coatings synthesized under these conditions also exhibited improved hardness, corrosion and wear resistance.
Synthesis of ti-al-xNb ternary alloys via laser-engineered net shaping for biomedical application: Densification, electrochemical and mechanical properties studies.
(MDPI, 2022-01-12) Kanyane, Lehlogonolo Rudolf; Popoola, Abimbola Patricia Idowu; Pityana, Sisa; Tlotleng, Monnamme
The lives of many people around the world are impaired and shortened mostly by cardiovascular diseases (CVD). Despite the fact that medical interventions and surgical heart transplants may improve the lives of patients suffering from cardiovascular disease, the cost of treatments and securing a perfect donor are aspects that compel patients to consider cheaper and less invasive therapies. The use of synthetic biomaterials such as titanium-based implants are an alternative for cardiac repair and regeneration. In this work, an in-situ development of Ti-Al-xNb alloys were synthesized via laser additive manufacturing for biomedical application. The effect of Nb composition on Ti-Al was investigated. The microstructural evolution was characterized using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). A potentiodynamic polarization technique was utilized to investigate the corrosion behavior of TiAl-Nb in 3.5% NaCl. The microhardness and corrosion behaviour of the synthesized Ti-Al-Nb alloys were found to be dependent on laser-processing parameters. The microhardness performance of the samples increased with an increase in the Nb feed rate to the Ti-Al alloy system. Maximum microhardness of 699.8 HVN was evident at 0.061 g/min while at 0.041 g/min the microhardness was 515.8 HVN at Nb gas carrier of 1L/min, respectively.
Performance evaluation of zinc anodes for cathodic protection of mild steel corrosion in HCL.
(Elsevier B.V., 2019-09-11) Loto, Cleophas Akintoye; Loto, RolandTolulope; Popoola, Abimbola Patricia
An assessment of performance of zinc anodes on the cathodic protection of mild steel in 0.5 M hydrochloric acid was made at both the room and elevated temperatures. The cathodic protection reactions process was evaluated by weight-loss method, corrosion rate calculation and potential measurement methods. The effectiveness of zinc sacrificial an- odes were found to be cathodically protective on mild steel in the hydrochloric acid at both the room temperature (27 °C) and elevated temperature (60 °C). There was close correlation of the results obtained for the weight-loss method and potential measurement in the HCL.
Physical beneficiation of heavy minerals – Part 1: A state of the art literature review on gravity concentration techniques.
(Elsevier Ltd., 2023-08-02) Nzeh, Nnaemeka Stanislaus; Popoola, Patricia; Okanigbe, Daniel; Adeosun, Samson; Adeleke, Abraham
The efficiency of physical separation techniques of heavy minerals usually encounters some setbacks. The reason is often not far from the inability to develop suitable mineral characterization strategies in order to comprehend/evaluate certain physicochemical features such as surface chemistry, specific gravity difference, magnetic and electrical responses distributed among the mineral particles. The intense need for the development/advancement of efficient gravity concentration route on heavy minerals, more especially for the recovery and upgrade of fine, neardense, low-grade heavy mineral deposits cannot be over-emphasized. However, the process application of gravity concentration on heavy minerals has not been widely investigated and has often times been neglected. Existing literature on investigations conducted does not completely incorporate process routes, operating principles, parameters and applications; and as such, information in this area is somewhat scanty, hence the purpose of this study. A bulk of more recently developed gravity concentration medium such as enhanced gravity concentrations possess essential potentials which can be applied in certain physical beneficiation routes. On this premise, the need for further investigation is highly imperative. This review is therefore aimed at revealing the advantageous features of enhanced gravity concentrations over the conventional techniques, as well as the process selection for optimal beneficiation and high-grade yields. Thus, process applications, operating mechanism/principles, general performance evaluation in treating/ upgrading heavy minerals using gravity techniques, the merits/shortcomings involved in conventional/enhanced gravity concentrators and recommendations have been captured in this review. This study will thus contribute greatly to the body of knowledge in the physical treatment/ concentration of heavy minerals.
Investigation of the effects of selected bio-based carburising agents on mechanical and microstructural characteristics of gray cast iron.
(Elsevier Ltd., 2020-02-12) Salawu, Enesi Y.; Ajayi, Oluseyi O.; Inegbenebor, Anthony O.; Akinlabi, Stephen; Akinlabi, Esther; Popoola, A.P. I.; Uyo, U.O.
The mechanism of graphite formation on gray cast iron metal during carburisation process using organic nanocarbon (ONC) was investigated at 900 C for a holding time of three (3) hours. TEM and XRD were employed to characterize the pulverised nano-carbon to determine their phases and bonding potentials. Also, SEM/EDS, XRD and Vickers’ hardness tester were employed to determine the microstructure, phase compositions as well as hardness and wear properties of the carburised material. The microstructural result showed that, there was uniform carbon diffusion into the substrate material which led to layers of graphite formation and subsequent surface modifications for each of the selected nano-carbon used. Also, the XRD results revealed variations in the peak patterns for each of the substrate carburised with different organic carbon with substrates showing graphite and iron phases as observed in that carburised in pulverised palm kernel shell having broad peaks at 35.50o, 44.4o, 65.12o and 82.395o. This is traceable to amorphous properties and crystalline behaviour of the organic carbon. Further to this, the micro-hardness measurement showed that substrate carburised using pulverised palm kernel shell performed better compared to other substrates in other media with a micro hardness value of 355.8 (HV) against as received which is 116.9 (HV). Thus, this is a novel and possible method of improving the properties of grey cast iron to meet the increasing demand in gear applications.
Physical beneficiation of heavy minerals – Part 1: A state of the art literature review on gravity concentration techniques.
(Elsevier Ltd., 2023-08-02) Nzeh, Nnaemeka Stanislaus; Popoola, Patricia; Okanigbe, Daniel; Adeosun, Samson; Adeleke, Abraham
The efficiency of physical separation techniques of heavy minerals usually encounters some setbacks. The reason is often not far from the inability to develop suitable mineral characterization strategies in order to comprehend/evaluate certain physicochemical features such as surface chemistry, specific gravity difference, magnetic and electrical responses distributed among the mineral particles. The intense need for the development/advancement of efficient gravity concentration route on heavy minerals, more especially for the recovery and upgrade of fine, near dense, low-grade heavy mineral deposits cannot be over-emphasized. However, the process application of gravity concentration on heavy minerals has not been widely investigated and has often times been neglected. Existing literature on investigations conducted does not completely incorporate process routes, operating principles, parameters and applications; and as such, information in this area is somewhat scanty, hence the purpose of this study. A bulk of more recently developed gravity concentration medium such as enhanced gravity concentrations possess essential potentials which can be applied in certain physical beneficiation routes. On this premise, the need for further investigation is highly imperative. This review is therefore aimed at revealing the advantageous features of enhanced gravity concentrations over the conventional techniques, as well as the process selection for optimal beneficiation and high-grade yields. Thus, process applications, operating mechanism/principles, general performance evaluation in treating/ upgrading heavy minerals using gravity techniques, the merits/shortcomings involved in conventional/enhanced gravity concentrators and recommendations have been captured in this review. This study will thus contribute greatly to the body of knowledge in the physical treatment/ concentration of heavy minerals.
2D computational modelling of thermo-mechanical behaviour of TiAl based alloys during application.
(Elsevier Ltd., 2022-02-22) Kanyane, L.R.; Raji, S.A.; Popoola, A.P.I.; Pityana, S.L.; Tlotleng, M.
The paper aims to study the thermo-mechanical analysis of a two-dimensional (2D) convex structural design sensitivity for typical engineering component application. COMSOL Multiphysics 5.3a was used to analyze the stress distribution, displacement along with thermal distribution of the component during high temperature application. The computational model incorporate two physics of solid mechanics and heat transfer in solids. A fine mesh size was applied on the component geometry which gives a high accuracy of the simulation results. The computational model results showed minimal displacement (12.14 104 m) of the Ti4822 alloy modelled under high temperature application. The model results also presented maximum stress concentration of 1.83 108 N/m2. A future paper will address 3D design sensitivity analysis in linear structural problems of titanium aluminide alloys during application.
The effect of annealing temperature on the microstructure, mechanical and electrochemical properties of arc-melted AlCrFeMnNi equi-atomic high entropy alloy
(Elsevier B.V., 2020-04-04) Masemola, Khumo; Popoola, Patricia; Malatji, Nicholus
In this work, an equiatomic AlCrFeMnNi high entropy alloy (HEA) was fabricated through an arc-melting and casting process. As-cast alloy ingot was annealed for 2 h at various temperatures to investigate the effect of heat treatment temperature on the microstructure, mechanical performance and electrochemical behaviour of the alloy. The morphology of the as-cast HEA consisted of interdendritic rich-Al + Ni BCC (B2) phase and majority dendriticmatrix consisting largely of rich-Cr BCC phase. Annealing higher than 400◦C, promoted the formation of FCC structure which increased in volume to 800◦C. Increase in heat treatment temperature coarsened the grains leading to a decrease in hardness and increase in coefficient friction. A good combination of strength and ductility was observed when annealing was performed at 600◦C. Anticorrosion properties were improved after annealing. However, high temperature annealing lowered corrosion resistance due to the galvanic effect. The alloys demonstrated high corrosion rate in acidic condition.
Surface effect of environmentally assisted corrosion growth of automotive welded steel performance.
(Elsevier Ltd., 2020-08-09) Fayomi, Ojo Sunday Isaac; Samuelb, Olusegun David; Mashilo, Matsobane; Popoola, Abimbola Patricia; Agboola, Oluranti; Balasubramanian, Dhinesh
Failure of steel in automobile industries due to environmentally assisted medium in service is alarming. In this study an effort has been made to investigate critically the corrosion induced performances of automotive welded part. The experimental correlation on the effect of corrosive media (NaCl and HCl solutions) on the base metal, heat affected zone (HAZ) and weld metal formed were examined using linear potentiodynamic polarization technique. The hardness, microstructural and phase rationale of the studied joint was evaluated using, diamond base indenter, Scanning electron microscope and x-ray diffractograms respectively. The results revealed that the base metal has no detrimental phase transformation unlike the HAZ and the weld joint region. The hardness value of 185 HV welded joint was obtained compared to 235.95 HV of base region. The corrosion propagation in the 3.5NaCl and 1 M HCl shows that pitting deterioration occurs at the welded position in all case as a result of the shift in grain refinement and micro-straining during welding process.
2D computational modelling of thermo-mechanical behaviour of tiAlbased alloys during application.
(Elsevier Ltd., 2022-02-25) Kanyane, L.R.; Raji, S.A.; Popoola, A.P.I.; Pityana, S.L.; Tlotleng, M.
The paper aims to study the thermo-mechanical analysis of a two-dimensional (2D) convex structural design sensitivity for typical engineering component application. COMSOL Multiphysics 5.3a was used to analyze the stress distribution, displacement along with thermal distribution of the component during high temperature application. The computational model incorporates two physics of solid mechanics and heat transfer in solids. A fine mesh size was applied on the component geometry which gives a high accuracy of the simulation results. The computational model results showed minimal displacement (12.14 104 m) of the Ti4822 alloy modelled under high temperature application. The model results also presented maximum stress concentration of 1.83 108 N/m2. A future paper will address 3D design sensitivity analysis in linear structural problems of titanium aluminide alloys during application.
Microstructural evolution and mechanical properties of pure titanium powders processed by spark plasma sintering.
(Elsevier B.V., 2019-01-07) Motsi, Glenda T.; ;Guillemet-Fritsch, Sophie; Chevallier, Geoffroy; Shongwe, Mxolisi B.; Olubambi, Peter A.; Estournes, Claude
In this study the effect of sintering pressure on the densification, microstructure and mechanical properties of commercial pure titanium (CP-Ti) powders with varying chemistry was investigated. The sintering was performed at a constant dwell time of 3 min at varying temperature and pressure in the range of 550–900 °C and 25-75 MPa in vacuum, respectively. Full densification with high Vickers hardness values of 340 HV and 262 HV was obtained at 25 MPa at 800 °C and 900 °C respectively for two commercial powders with different average particles sizes. Different microstructural transformations with respect to increasing temperature and pressure were observed on the sintered pellets. The results were discussed emphasizing the huge role of the interstitial elements, contained in the starting powders, on the properties (relative density, Vickers hardness and microstructure) of the dense samples. This paper shows that good mechanical properties can be obtained by SPS technique when CP-Ti powders are sintered at very low temperature during a short period in contrast to conventional fabrication techniques.
Electrochemical study and gravimetric behaviour of gray cast iron in varying concentrations of blends as alternative material for gears in ethanol environment.
(Elsevier B.V., 2020-06-05) Salawu, Enesi Y.; Ajayi, Oluseyi O.; Inegbenebora, Anthony O.; Akinlabi, Stephen; Popoola, A.P.I.; Akinlabi, Esther; Omotosho, Olugbenga A.; Uyo, U.O.
The phenomenon of chemical degradation of mild steel materials under ethanol environment is becoming alarming. In order to study the electrochemical, thermal and mechanical behaviour of gray cast iron in this environment, this paper deals with the investigation of gray cast iron sample in varying concentrations of different ethanol blend solution. The electrochemical behaviour of gray cast iron sample was studied in ethanol concentrations of A – 42%, B – 40%, C – 28%, D – 43% and E – 45% using distilled water as control medium. Observations of the microstructures after the test showed that mainly oxides and corrosion products dominate the surfaces. However, some areas showed some cracks which are less severe. Also, the thermal gravimetric analyses of samples after the electrochemical test showed that, there was reduced thermal decomposition which suggests its good performance for gear application. Further to this, the micro-hardness results showed that the material maintained its mechanical properties despite the interactions with the solvents
Magnesium-based composite by nano-nucleation of b-Mg17Al12 using spark plasma sintering route for advanced structural application.
(Elsevier B.V., 2023-03-17) Fayomi, J.; Popoola, A.P.I.; Popoola, O.M.; Aigbodon, V.S.
The influence of nano AlN on the microstructural evolution, mechanical (nanohardness, elastic modulus, microhardness, tensile, and yield strength), and tribological performance were examined. The outcome of the research suggested that the AlN inclusion at varying fraction have a direct connection to the enhancement of the investigated properties and a maximum result was achieved by the MgAZ91D-12 wt%AlN nanocomposite. The scanning electron microscope shows the nucleation and dissolution of the dominant b-Mg17Al12 found in the monolithic MgAZ91D following the addition of nano-AlN. Maximum microhardness of 84.0 ± 0.21 HV, nanohardness of 2.2 ± 0.037 GPa, the elastic modulus of 58.333 ± 0.26 GPa, elastic recovery (We/Wt) of 0.228, elastic strain to failure (H/Er) of 0.040, yield pressure (H3/Er 2) of 0.0035 GPa, and the lowest plasticity index (Wp/Wt) of 0.7362 were achieved by MgAZ91D-12 wt%AlN. The wear rate of the sintered composite increases with the increase in the load applied but decreases with an increase in the percentage weight fraction of the nano AlN. The coefficient of friction result is observed to be high in unreinforced alloy and decreases as a function of the nano inclusion and the applied load.

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