Metallurgical and Materials Engineering- Scholarly Publications
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- ItemOpen AccessImprovement on the strength of 6063 aluminum alloy by means of solution heat treatment(Materials Science and Technology (MS&T), 2006) Esezobor, D.E.; Adeosun, S.O.The paper examines the solution heat treatment of an extruded 6063 aluminum alloy. The study shows that the strength and fracture resistance of this metal alloy can be influenced to an appreciable extent by the solution heat treatment used in this investigation. The ultimate tensile strength (UTS) increases as the solution time increases from 6 to 20 hours for treatment temperature of 90oC. The maximum UTS (198.8MPa and 188.6 MPa) occur at 120oC and 150oC respectively at the solution holding time of 10hours. While, at 120oC and 10hrs, the UTS are relatively the same as the as-received specimen, though the latter exhibits a higher fracture stress. Annealing at 470oC results to lower UTS value (114.3MPa) and poor fracture resistance (522MPa). The results of the experiment are found to be in near perfect agreement with Voce Empirical Model. These observations have shown that solution treatment at 150oC for 10 hrs can produce significant plastic flow before fracture of 6063 aluminum alloys. Irrespective of the treatment process adopted, the stress- strain behavior is essentially the same for strains within the range 0 􀂔 􀄰 􀂔 0.005.
- ItemOpen AccessStress variation in deep drawn 1017 aluminum alloy(Journal of Materials Engineering and Performance, 2007) Balogun, S.A.; Adeosun, S.O.; Esezobor, D.E.The qualitative analysis of the elastic-plastic behavior of metal sheet is usually performed by finite element methods. These methods are often complicated because of large computational requirements associated with the use of realistic models. In this paper, an effective model based on the macro-mechanical properties of the metal blank and tool geometry is used to describe the anisotropic plastic flow of the metal sheet in plane stress condition. The model is derived from the fundamental deflection equation of beam/column. The model used to optimize the stamping process is designed to be as close to realistic forming conditions as possible.
- ItemOpen AccessEffects of Deformation Processing on the Mechanical Properties of Aluminum Alloy 6063(The Minerals, Metals & Materials Society and ASM International 2007, 2007) Balogun, S.A.; Esezobor, D.E.; Adeosun, S.O.Aluminum alloy 6063 was processed by upset forging and cold rolling at ambient temperature. The tensile, ductile, and hardness (HRN) properties of the samples were studied. Upset forging is determined from the processing of this alloy to obtain maximum ultimate tensile strength (UTS) and HRN. At room temperature, the UTS and HRN increase as the range of reduction from processing increases from 0 to 50 pct. However, the ductility decreases correspondingly, which is indicative of a low strain-hardening exponent. The gaseous pores in the as-cast structure spread when forged, while the rolling had no effect on this casting defect. The pore elongation and thinning promoted superior strength, HRN, and ductility in the forged sample, as compared to the cold-rolled sample.
- ItemOpen AccessEffects of Deformation Processing on the Mechanical Properties of Aluminum Alloy 6063(The Minerals, Metals & Materials Society and ASM International, 2007) Balogun, S.A.; Esezobor, D.E.; Adeosun, S.O.Aluminum alloy 6063 was processed by upset forging and cold rolling at ambient temperature. The tensile, ductile, and hardness (HRN) properties of the samples were studied. Upset forging is determined from the processing of this alloy to obtain maximum ultimate tensile strength (UTS) and HRN. At room temperature, the UTS and HRN increase as the range of reduction from processing increases from 0 to 50 pct. However, the ductility decreases correspondingly, which is indicative of a low strain-hardening exponent. The gaseous pores in the as-cast structure spread when forged, while the rolling had no effect on this casting defect. The pore elongation and thinning promoted superior strength, HRN, and ductility in the forged sample, as compared to the cold-rolled sample.
- ItemOpen AccessEffects of Heat Treatment on Strength and Ductility of Rolled and Forged Aluminum 6063 Alloy(Vol. 9, No.8, pp.763-773, 2010 jmmce.org Printed in the USA. All rights reserve, 2010) Adeosun, S.O.; Balogun, S.A.; Sekunowo, O.I.; Usman, M.A.This work examines the effect of heat treatment on tensile strength and ductile responses of rolled and forged AA6063 aluminum alloy. Some cast samples were rolled while some were forged at ambient temperature (320C). The deformed samples were subjected to heat treatment processes. The tensile strengths of rolled (212 MPa) and forged (127 MPa) samples are enhanced at ambient temperature but with poor elongation responses. A combination of improved strength and elongation (127 MPa, 24%) can be obtained in rolled sample when solution heat treatment (SHT) is applied after deformation and cooling in water. The forged sample when homogenized, solution treated and water quenched has elongation of about 24% with improved strength of 137 MPa. These results were obtained because of the development of very fine AlFeSi texture in the matrix and along the grain boundaries.
- ItemOpen AccessInfluence of magnesium addition on the mechanical and corrosion responses of 7249 aluminum alloy(Journal of Corrosion Science and Engineering, 2010-11) Adeosun, S.O.; Sekunowo, I.O.; Balogun, S.A.; Oladoye, A.M.; Osoba, L.O.The effects of 1.8-2.6% Magnesium addition on the mechanical and corrosion responses of 7249 aluminum alloy have been studied. Samples of the alloy in as-cast, T6 and RRA forms were made and subjected to tensile and hardness tests. Exfoliation, ferric-chloride and immersion corrosion analyzes were also carried out on the alloy forms. The results show that strength and hardness increased at the expense of ductility as the Mg content is increased to 2.6 %. RRA form exhibited the best tensile and hardness properties coupled with superior corrosion resistance. This characteristic behaviour of RRA form is predicated on the precipitation of coherent and stable equilibrium MgZn2 phase.
- ItemOpen AccessEffect of Deformation on the Mechanical and Electrical Properties of Aluminum-Magnesium Alloy(Journal of Minerals & Materials Characterization & Engineering., 2011) Adeosun, S.O.; Sekunowo, O.I.; Balogun, S.A.; Osoba, L.O.This paper presents the effect of deformation on the tensile strength, toughness, hardness and electrical resistance of aluminum 6063 alloy. Cast samples were cold rolled in the range of 0-24 percent thickness reduction and subjected to mechanical (static, dynamic) and electrical resistance tests. Results show significant improvement in hardness and electrical resistance properties of the alloy. The nature, amount and distribution of the secondary phase, Mg2Si, particles precipitated within the matrix which was influenced by the extent of cold-work, are responsible for the observed behaviour. The resistance of the alloy also depends on the degree of cold work carried out p
- ItemOpen AccessEffect of Deformation on the Mechanical and Electrical Properties of Aluminum-Magnesium Alloy(Journal of Minerals & Materials Characterization & Engineering, 2011) Adeosun, S.O.; Sekunowo, O.I.; Balogun, S.A.; Osoba, L.O.This paper presents the effect of deformation on the tensile strength, toughness, hardness and electrical resistance of aluminum 6063 alloy. Cast samples were cold rolled in the range of 0-24 percent thickness reduction and subjected to mechanical (static, dynamic) and electrical resistance tests. Results show significant improvement in hardness and electrical resistance properties of the alloy. The nature, amount and distribution of the secondary phase, Mg2Si, particles precipitated within the matrix which was influenced by the extent of cold-work, are responsible for the observed behaviour. The resistance of the alloy also depends on the degree of cold work carried out prior to use.
- ItemOpen AccessEffect of Cu and Zn Addition on the Mechanical Properties of Structural Aluminum Alloy(Journal of Modern Manufacturing Technology., 2011) Adeosun, S.O.; Balogun, S.A.; Osoba, L.O.; Ayoola, W.A.; Oladoye, A.M.The effect of independently adding Cu and Zn on the mechanical properties of 6063 aluminium alloy has been examined. In this study, sand cast samples of aluminum alloy containing Cu/Zn (0-20 vol %) and homogenized at 5100C for 1hr are analyzed for ultimate tensile strength (UTS), hardness, elongation and impact energy. Addition of more than 15 vol % Zn to structural aluminum alloy raised its hardness and elongation. Copper additions above 4 vol % lowered the UTS, elongation and impact energy. However, the hardness increases with percent addition of Cu. These properties are functions of evolving microstructure. The intermetallic compound of Zn-Al has structure and crystal orientation similar to Mg2Si in the matrix with its influence on the aluminum alloy similar to that of Mg2Si. This occurrence is the reverse of the effect of Cu on the alloy. The addition of zinc to structural aluminum will improve the homogeneity of the matrix. The impact energy and hardness of the matrix are enhanced when Cu addition is within 2-4 vol %.
- ItemOpen AccessOn preventing HAZ cracking in laser welded DS Rene 80 superalloy(Institute of Materials, Minerals and Mining, 2011) Osoba, L.O.; Sidhu, R.K.; Ojo, O.A.The heat affected zone (HAZ) cracking behaviour in a laser beam directionally solidified (DS) Rene 80 nickel based superalloy subjected to preweld heat treatments was studied. The HAZ cracks in the alloy are grain boundary liquation cracks caused by liquation reaction of both nonequilibrium secondary solidification product, MC carbides and equilibrium solid state reaction product, c9 precipitates. In contrast to theoretical prediction based a preweld heat treatment that reduced grain boundary liquid film thickness did not result in a lower HAZ cracking, which can be related to concomitant reduction in the ability of the base alloy to relax welding stress. In addition, formation of intergranular M5B3 boride particles in preweld alloy appeared to have aided cracking susceptibility by lowering grain boundary liquation temperature and widening the brittle temperature range in the HAZ during cooling. Based on the analysis of the results, application of a new preweld heat treatment that prevents the formation of the intergranular borides and induces moderate base alloy hardness resulted in a nearly crack free HAZ in laser welded DS Rene 80 superalloy
- ItemOpen AccessReliability assessment of offshore jacket structures in Niger Delta(Petroleum & Coal, 2011) Salau, M.A.; Esezobor, D.E.; Omotoso, M.F.Jacket platform is essential for continuous crude oil production in Nigerian offshore oil and gas fields. However, the structures are constantly exposed not only to hostile environment and operational conditions but as well as seawater that consists of salty and oxygenated water with high pH level that accelerates corrosion process. This phenomenon leads structural members to reduction in thickness with time. The application of the available computer software used for offshore structural assessment, simply give data about the structural member strength with no information regarding structural system reliability. In this paper, a time-variant formulation technique for the accurate estimation of corroded jacket structural system reliability is derived and presented by utilizing series and parallel reliability theories. The results of the study established that the reliability of a jacket structures is the product of bracings and legs reliabilities and this value decreases with platform age.
- ItemOpen AccessEffect of Deformation on the Mechanical and Electrical Properties of Aluminum-Magnesium Alloy(Journal of Minerals & Materials Characterization & Engineering, 2011) Adeosun, S. O.; Sekunowo, O. I.; Balogun, S. A.; Osoba, L.O.This paper presents the effect of deformation on the tensile strength, toughness, hardness and electrical resistance of aluminum 6063 alloy. Cast samples were cold rolled in the range of 0-24 percent thickness reduction and subjected to mechanical (static, dynamic) and electrical resistance tests. Results show significant improvement in hardness and electrical resistance properties of the alloy. The nature, amount and distribution of the secondary phase, Mg2Si, particles precipitated within the matrix which was influenced by the extent of cold-work, are responsible for the observed behaviour. The resistance of the alloy also depends on the degree of cold work carried out prior to use.
- ItemOpen AccessSuitability of Nigerian Rocks as Refractory Materials for Monolithic Furnace Lining(Particulate Science and Technology: An International Journal, 2012) Osoba, L.O.; Afolabi, A.S.The physical, chemical composition and service properties of imported monolithic refractory and locally produced refractory lining materials were investigated and compared in this study. The samples were compacted in a standard rammer, cured in air for 24 h and oven dried for 24 h. They were then heated to temperature of 100 C and characterized to determine their refractory properties. These samples were tested for parameters, such as bulk density, porosity, thermal conductivity, electrical conductivity, refractoriness, permeability, and cold strength. The results obtained indicate that local acidic ramming mass was found to be a good substitute to imported ramming masses due to comparative properties of the former. A fusion temperature of 1620 C was obtained in the local sample which is equivalent to the value obtained for the imported ramming masses. The results of other properties show little or no variation between the locally produced ramming mass and the imported ones.
- ItemOpen AccessEffect of casting mould on mechanical properties of 6063 aluminium alloy(Journal of Engineering Science and Technology, 2012) Ayoola, W.A.; Adeosun, S.O.; Sanni, O.S.; Oyetunji, AModern production methods for casting articles include the use of sand- mould, metal-mould, die, and centrifugal castings. Castings produced using sand mould is known to have peculiar microstructures depending on average size, distribution and shape of the moulding sand grains and the chemical composition of the alloy. These affect the surface finish, permeability and refractoriness of all the castings. In this paper, the effect of using CO2 process, metal mould, cement-bonded sand mould and naturally-bonded sand mould on the hardness, tensile and impact strengths of as-cast 6063 Aluminum alloy is presented. The results show that there is significant increase in hardness (33.7 HB) of the alloy when naturally-bonded sand mould is used for its production over that of metal, CO2 and cement moulds. The stress-strain curves behaviour of the samples also indicated that sample from naturally bonded sand has highest tensile strength with superior ductility. The alloy shows highest impact strength when metal mould is used for sample preparation in comparison with other moulds.
- ItemOpen AccessInvestigation into the Deep Drawability of 0.1%C Eutectoid Steel(Journal of Minerals and Materials Characterization and Engineering., 2012) Adeosun, S.O.; Sekunowo, O.I.; Balogun, S.A.The phenomenon of anisotropism in most rolled products necessitates that the rolling direction that enhances desirable mechanical property is established. In this paper, the comparative deep drawability of as-received and annealed mild steel containing about 0.1%C was investigated. The flat steel sample was divided into two and classified as as-received and heat treated respectively. The heat treated sample was obtained by annealing at 950˚C after been soaked for 5 hours and deep drawn at ambient temperatures (35˚C - 42˚C). From both samples, circular specimens were machine- blanked parallel to the rolling directions inclined at 0˚, 45˚ and 90˚ respectively and were prepared for deep drawability test while rectangular specimens were prepared for tensile test. Both specimens, as-received and annealed were then subjected to tensile, cupping and microstructural analyses. Results show that the contribution to increased formability at 90° rolling direction seems to have come from the spheroid-like pearlite grains induced during annealing while the stability of spread observed was achieved through a modest increase in strength. Thus, the resistance of annealed eutectoid steel to cupping is quite minimal at 90° to the rolling direction. The desirable drawability characteristics developed by the annealed eutectoid steel specimen are: cup-height, 30 mm maximum and ear, 6.4% maximum.
- ItemOpen AccessStudy on the mechanical properties of cast 6063 al alloy using a mixture of aluminum dross and green sand as mold(The Journal of The Minerals, Metals & Materials Society (TMS), 2012) Adeosun, S.O.; Sekunowo, S.I.; Balogun, S.A.; Obembe, O.O.The mechanical characteristics of 6063 aluminum alloy cast in a mixture of aluminum dross and silica sand as mold have been examined. The amount of dross in the green silica sand was varied in the range of 0–80% with bentonite as binder. In all, 40 samples were cast, and 8 of these were left in the as-cast condition for control while 32 were first homogenized at 470 C for 6 h and then rolled in a two-high mill at ambient temperature to 10% reduction in one pass. The rolled samples were solution heat treated at 515 C for 8 h followed by normalizing, annealing, and quench tempering, respectively. The samples were then simulated and tensile behavior coupled with the evaluation of microhardness and microstructures developed. The results obtained demonstrate significant improvement in mechanical properties from 50% to 80% dross in the mold. Tensile strength increased to 177 MPa and 15% elongation compared with conventional 6063-T5 aluminum alloy with 145 MPa tensile strength and 8% elongation. The improvement in mechanical properties by the quench-tempered samples can be attributed to the inducement of fine and coherent Mg2Si crystals within the matrix. Furthermore, the overall analysis of the proportion of dross to the size of cast show that about 64% of dross generated can be utilized as mold material.
- ItemOpen AccessImproved Resistance to Laser Weld Heat-Affected Zone Microfissuring in a Newly Developed Superalloy HAYNES 282(The Minerals, Metals & Materials Society and ASM International, 2012) Osoba, L.O.; Ding, R.G.; Ojo, O.A.Gleeble thermomechanical simulation and microstrucutural analyses of laser beam weldability of a newly developed precipitation-hardened nickel-base HAYNES alloy 282 were performed to better understand the fundamental cause of heat-affected zone (HAZ) cracking and how to prevent the cracking problem in the material. Submicron size intergranular M5B3 particles are identified for the first time in the present work by transmission electron microscopy, and were found to be the primary cause of HAZ grain boundary liquation cracking in the alloy. Complete dissolution of the liquating M5B3 particles by preweld heat treatment exacerbated rather than reduced susceptibility to cracking, which could be attributed to nonequilibrium intergranular segregation of boron atoms, liberated by the complete dissolution of the boride particles, during cooling from heat treatment temperature. Consequently, to reduce the HAZ cracking, a preweld heat treatment that reduces the volume fraction of the M5B3 particles while minimizing nonequilibrium grain boundary boron segregation is necessary, and this is possible by heat treating the alloy at 1353 K to 1373 K (1080 C to 1100 C). Further improvement in cracking resistance to produce crack-free welds is achieved by subjecting the alloy to thermomechanically induced grain refinement coupled with the preweld heat treatment at 1353 K (1080 C). A Gleeble hot ductility test showed that formation of the crack-free welds is unexplainable by mere reduction in grain size without considering the effect of grain refinement on intergranular liquid produced by subsolidus liquation of the M5B3 borides. DOI: 10.1007/s11661-012-1212-7
- ItemOpen AccessMechanical Characteristics of 6063 Aluminum-Steel Dust Composite(International Scholarly Research Network ISRN Mechanical Engineering, 2012) Adeosun, S.O.; Akpan, E.I.; Sekunowo, O.I.; Ayoola, W.A.; Balogun, S.A.Studies on the effect of steel dust (EAF dust) addition on the mechanical properties of 6063 Aluminium alloy have been carried out. The cast composite samples contain steel dust from 2–20 wt% produced in sand mould. These cast samples were homogenized, cold rolled, and solution-treated. The solution treated samples were normalized in still air, some quenched in water while some were tempered after quenching. Tensile and hardness responses were determined in all these processed samples. The results obtained reveal that 10 wt% steel dust in aluminium 6063 improved the ultimate tensile strength to 111.09 MPa and a corresponding hardness of 51.2 HV. Microstructural analysis shows iron containing intermetallics which are well distributed in the matrix with its morphology depending on the heat treatment and deformation imposed on them. Tensile strength and hardness of the composites was also found to depend on the volume fraction of intermetallics in the matrix.
- ItemOpen AccessCorrosion Behaviour of Heat-Treated Aluminum-Magnesium Alloy in Chloride and EXCO Environments(Hindawi Publishing Corporation International Journal of Corrosion, 2012) Adeosun, S.O.; Balogun, S.A.; Obiekea, V.D.; Sekunowo, O.I.Machines designed to operate in marine environment are generally vulnerable to failure by corrosion. It is therefore imperative that the corrosion susceptibility of such facilities is evaluated with a view to establishing mechanism for its mitigation. In this study, the corrosion behaviour of as-cast and retrogression-reagion (RRA) specimens of aluminum alloy containing 0.4–2.0 percent magnesium additions in NaCl, FeCl3, and EXCO solutions was investigated. The corrosion simulation processes involved gravimetric and electrochemical techniques. Results show substantial inducement of Mg2Si precipitates at a relatively higher magnesium addition, 1.2–2.0 percent, giving rise to increased attack. This phenomenon is predicated on the nature of the Mg2Si crystals being anodic relative to the alloy matrix which easily dissolved under attack by chemical constituents. Formation of Mg2Si intermetallic without corresponding appropriate oxides like SiO2 and MgO, which protect the precipitates from galvanic coupling with the matrix, accentuates susceptibility to corrosion.
- ItemOpen AccessMechanical Response of Al-1.09Mg2Si Alloy under Varying Mould and Thermal Ageing Conditions(Hindawi Publishing Corporation Journal of Metallurgy Volume 2012, Article ID 921235, 7 pages, 2012) Sekunowo, O.I.; Lawal, G.I.; Adeosun, S.O.Samples of the 6063 (Al-1.09Mg2Si) alloy ingot were melted in a crucible furnace and cast in metal and sand moulds, respectively. Standard tensile, hardness, and microstructural test specimens were prepared from cast samples, solution treated at 520◦C, soaked for 6 hrs, and immediately quenched at ambient temperature in a trough containing water to assume a supersaturated structure. The quenched specimens were then thermally aged at 175◦C for 3–7 hrs. Results show that at different ageing time, varied fractions of precipitates and intermetallics evolved in the specimens’ matrices which affect the resulting mechanical properties. The metal mould specimens aged for four hours (MTA-4) exhibited superior ultimate tensile strength of 247.8 MPa; microhardness, 68.5 HV; elongation, 28.2% . It is concluded that the extent of improvement in mechanical properties depends on the fractions, coherence, and distribution of precipitates along with the type of intermetallics developed in the alloy during ageing process.