scholarly works
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Item Production and characterisation of Al-Mg-Cr alloy for machine tool applications(2020-08) Ajide, O. O.; Ogochkwu, C. D.; Akande, I. G.; Petinrin, M. O.; Ismail, O. S.; Oluwole, O. O.; Oyewola, O. M.Industrialisation and technological advancement are immensely influenced by materials development and innovation. Recent studies have shown that the use of some specialised alloying elements can be explored for enhancing properties of monolithic alloys. This study focuses on the production and characterisation of Al-Mg-Cr alloy suitable for machine tool applications. Al-Mg-Cr alloy was developed using sand mould and two-step stir-casting method. Chromium was added to Al-Mg alloy at varying contents of 0.5, 1.0, 1.5 and 2.0 %. Tensile tests were carried out in accordance with ASTM E8 to determine ultimate tensile strength (UTS), percentage elongation and modulus of elasticity at varying chromium contents. The evolved microstructures were examined using an optical microscope (OPM). The study revealed that the alloy containing 1.5% chromium exhibited maximum ultimate tensile strength of 135.15 MPa and percentage elongation of 3.76 %. However, Al-Mg-Cr alloy containing 1.0% chromium exhibited best combination of UTS (123.98 MPa), percentage elongation (3.32%), modulus of elasticity (12.11 GPa) and microstructural features. Five samples of Al-Mg-1.0Cr alloy were thereafter heat treated at different temperatures from 250 ˚C to 450 ˚C. The heat treated samples were also subjected to tensile tests and optical microscopy. The results were compared with the as-cast Al-Mg-1.0Cr alloy. The results showed that heat treatment of Al-Mg-Cr alloy had adverse effect on their mechanical and microstructural properties. The outcome of this study has shown that chromium as alloying element has potentials for enhancing tensile and microstructural characteristics of Al-Mg based alloys, and the benefit can be explored for machine tool applications.Item Microstructural characteristics of aluminum based composites developed by liquid metallurgyroute: an overview(2016-11) Ajide, O. O.; Oluwole, O. O.; Abu, R.; Petinrin, M. O.The extensive potential engineering applications of Aluminium Metal Matrix Composites (AMCs) are strong motivations for researchers renewed efforts in the development and characterisation of this class of material. The importance of microstructures for AMCs characterisation is enormous for reliable interpretations of its physical, mechanical, corrosion and thermal properties. Hence, a comprehensive review is quintessential in order to have a general overview of the influence and implications of microstructural characteristics on AMCs material properties. The review shows that an improved stir casting setup provides a reliable platform for effective and efficient stirring mechanism in the production of AMCs. This improved system is capable of reducing agglomerations to the barest minimum and thus promotes homogeneous dispersion of ceramic reinforcement particles in the matrix. The nature of AMCs microstructures have specific implications to its mechanical, corrosion and wear properties. The formation of pores, pits, rough surface and ceramics particles agglomerations in AMCs microstructures are manifestations of severe corrosion of the composites in different environments. The microstructural characteristics of corroded composite samples are aggravated by the harshness of the corrosion environments and increase in the percentage weight fractions of most ceramic reinforcement particles. The type of ceramic reinforcement particles used in AMCs has been well reported in the literature to have immense influence on its microstructural characteristics. Further, the review was able to show that heat treatment is a reliable process that can be explored in enhancing the homogeneous dispersion of reinforcement particles in AMCs matrix and its overall microstructural features. This review has enriched researchers’ understanding on immense benefits of AMCs microstructural examinations and its numerous implications. It is hopeful that this will be an illuminating platform for intensifying research activities on the microstructural characterisation of AMCs. The conclusion that can be drawn from this in-depth overview is that microstructural examinations will remain one of the leading techniques for AMCs materials properties characterisation. Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) will continue to be the domineering microstructural examinations techniques for characterising the material properties of AMCs.Item Comparative analysis of analytical and graphical upperbound solutions for 4-high reversing aluminium cold-rolling sheet mill(Scientific & Academic Publishing, 2012) Oluwole, O. O.; Adewumi, A. D.Upper bound solutions to a 4-High reversing aluminium cold-rolling sheet mill was obtained in this work using both analytical and graphical methods. The upper bound method was applied to the rolling of an Al 1200 sheet from 7mm to 0.6mm in six passes. It was observed that both methods were very effective in predicting upper bound load value with the graphical method giving a higher value using input velocity values from industry. However, it was observed that the graphical method becomes very difficult to use when sheet thicknesses become very small.Item Comparative study of corrosion behaviour of nickel and gold plated carbon steels used as ornamentals in saline environment(Science and Academic Publishing, 2012) Oluwole, O. O.; Garus-Alaka, W.; Ajide, O. O.This study investigated the corrosion resistance of plated and unplated steels useful as ornamentals in saline environment. Nickel plating of carbon steel was done in watts solution for 25minutes with a current density of 3 Adm-3 at 60oC. The nickel plated carbon steel was later gold plated for 20 minutes with a current density of 0.2 Adm-3 at 50oC . The plated and unplated carbon steels were immersed in saline environment for 360 hours. Weight loss was taken every 24 hours in order to evaluate corrosion penetration rate (CPR). The results obtained showed that plated carbon steel generally offers a better corrosion resistance than the unplated one. Corrosion of ornamentals is equally gaining importance especially coated ornamentals. The use of nickel for ornamentals is gaining more prominence over silver rising due to its shiny surface and its cost. The use of nickel plated ornamentals just as gold plated ornamentals are being patronized will surely become common place due to affordability for the generality of people. However, the effects of everyday corrosive fluids from kitchen salt and low acidic media on the durability of the coatings need to be established. Carbon steel is the natural substrate used in ornamental coatings .The results also showed that a small thickness of gold plated carbon steel exhibited better corrosion resistance in saline environment. More also, gold plated carbon steel is found to be more suitable and reliable candidate material than nickel plated carbon steel in this environment although with higher costs.Item Comparative analysis of analytical and graphical upperbound solutions for 4-high reversing aluminium cold-rolling sheet mill(Scientific & Academic Publishing, 2012) Oluwole, O. O.; Adewumi, A. D.Upper bound solutions to a 4-High reversing aluminium cold-rolling sheet mill was obtained in this work using both analytical and graphical methods. The upper bound method was applied to the rolling of an Al 1200 sheet from 7mm to 0.6mm in six passes. It was observed that both methods were very effective in predicting upper bound load value with the graphical method giving a higher value using input velocity values from industry. However, it was observed that the graphical method becomes very difficult to use when sheet thicknesses become very small.Item Comparative study of corrosion behaviour of nickel and gold plated carbon steels used as ornamentals in saline environment(Science and Academic Publishing, 2012) Oluwole, O. O.; Garus-Alaka, W.; Ajide, O. O.This study investigated the corrosion resistance of plated and unplated steels useful as ornamentals in saline environment. Nickel plating of carbon steel was done in watts solution for 25minutes with a current density of 3 Adm-3 at 60oC. The nickel plated carbon steel was later gold plated for 20 minutes with a current density of 0.2 Adm-3 at 50oC . The plated and unplated carbon steels were immersed in saline environment for 360 hours. Weight loss was taken every 24 hours in order to evaluate corrosion penetration rate (CPR). The results obtained showed that plated carbon steel generally offers a better corrosion resistance than the unplated one. Corrosion of ornamentals is equally gaining importance especially coated ornamentals. The use of nickel for ornamentals is gaining more prominence over silver rising due to its shiny surface and its cost. The use of nickel plated ornamentals just as gold plated ornamentals are being patronized will surely become common place due to affordability for the generality of people. However, the effects of everyday corrosive fluids from kitchen salt and low acidic media on the durability of the coatings need to be established. Carbon steel is the natural substrate used in ornamental coatings .The results also showed that a small thickness of gold plated carbon steel exhibited better corrosion resistance in saline environment. More also, gold plated carbon steel is found to be more suitable and reliable candidate material than nickel plated carbon steel in this environment although with higher costs.Item Effect of cold drawn deformation on mechanical properties of low carbon steel due to changes in grain size(2011-09) Raji, N. A; Oluwole, O. O.The effect of grain size on the mechanical properties of cold-drawn low carbon steel was investigated. Low carbonsteel specimen cold-drawn to 20%, 25%, 40% and 55% as applicable for the manufacture of 4 inches, 3 inches,21/2 inches and 2inches nail were obtained. The study was aimed at providing experimental result for the understanding of grain size effects which occur with increasing degree of cold-drawn deformation in low-carbon steel used for nail manufacture.The micrographs of steel were obtained using optical microscopy(OM) observation for 20%, 25%,40% and 55% degrees of drawn deformation. From the OM micrographs the counting method as stated in the ASTME E112 standard for grain size was used to determine the grain size of the steel on the micrograph at the different degrees of deformation. The tensile strength, yield strength, brinnel hardness, and toughness of the materials were obtained from mechanical tests. It was shown that the tensile strength, yield strength, toughness and hardness follow quite closely the hall-petch equation.Item Coal-fired power systems: oppportunities and challenges in the development of superalloys for boiler systems(2011) Oluwole, O. O.Coal fired power systems are still integral part of energy generation in many countries. The fact that this scenario will remain for quite sometime has accentuated the pursuit of clean coal initiatives (CCPI) aimed at getting to near zero(NZE)the carbon emissions in coal power generation. One of the major challenges in development of clean coal technology is in the area of materials technology for the development of boiler/steam turbine and Integrated Gasification Combined Cycle (IGCC) systems. As the most critical component in the construction of boiler systems, the superheater tubes have to undergo the most severe service conditions and must meet Stringent requirements with respect to fireside coal-ash corrosion/erosion, steamside oxidation and spallation, along with creep strength, thermal fatigue strength, and weldability. This paper presents the challenges of developing novel superalloys for these systems and the methods being advanced to overcome the problems.Item Phase field simulation for recrystallization kinetics of cold-drawn 0.12wt%C steel in full annealing(2014-03) Raji, N. A.; Oluwole, O. O.The importance of recrystallization kinetics in metal process cannot be over emphasized in providing information as to the control of microstructure of materials for purpose of improving or impacting desired mechanical properties in processed materials. In this study, 0.12wt% C steel cold drawn between 20% - 55% were graduallyheateduptoatemperatureof900°C followed bysoakingtreatment between 600 seconds and 3600 seconds in a Gallenkomp® mufflefurnace model SVL-1009 with voltage regulation of 220 V, 50 Hz of temperature range 300°C - 1000°C. The influence of the annealing process on the strength and impact toughness properties of the annealed steel were evaluated from tensile and charpy-impact tests conducted on the annealed steel. A phase field method is used to describe the recrystallization kinetics of the annealed cold drawn 0.12wt%C steel for the different degrees of cold drawn deformation. The experimental data obtained from the tensile and charpy-impact test were used as input data for the phase field simulation of the recrystallization process. The results show that the yield strength of the annealed cold drawn 0.12wt% C steel increases with increasing soaking time within the range of 600 sec.– 3600 sec. for the 20% cold drawn steel, between 600 sec.- 2400 sec. for the 25% and between 600 sec.-1800 sec. for the 40% and 55% cold drawn steel. The treatment increased the impact toughness of the steel for the 20%-40% cold drawn deformation but loses its toughness for the 55% cold drawn steel. The tensile strength however reduces for all the cold drawn steel irrespective of the degree of deformation. The simulation results show that reformation of grains in cold drawn 0.12wt%C steel depends on the degree of cold drawn deformation and the soaking time of annealing. The response of the mechanical properties of the annealed cold drawn 0.12wt% C steel therefore depends on the degree of cold deformation and soaking time of annealingItem Effect of iso-thermal treatment on the corrosion behaviour of low carbon steel (Nigerian C2R grade) in a buffered solution containing chloride and carbonate ions(2012) Atanda, P. O.; Olorunniwo, O. E.; Alabi, O. D.; Oluwole, O. O.This work has investigated the corrosion behavior of low carbon steel subjected to four different modes of iso-thermal heat treatment and then immersed in a neutral buffer corrosive medium containing carbonate and chloride ions. The low carbon steel material was cut into twenty small pieces of length 18±2mm, put in groups of five and subjected to: Annealing, Hardening, Normalizing and tempering, each corresponding to an iso-thermal mode of treatment. The samples were ground and polished, and micrographs taken for each mode of treatment. The samples were then immersed into the corrosion medium; a neutral buffer and samples were withdrawn for measurement every 72 hours. The experiment lasted 360 hours (15 days). The weight loss due to corrosion of the samples, the corrosion rate of the samples and the pH variation of the samples were monitored against time of exposure. It was observed that samples which had undergone tempering mode of heat treatment turned out to be the ones with the best corrosion resistance.