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Öğe Adhesive weld bonding of interstitial free steel at spot welding for automotive application(Redakcia Kovove Materialy, 2010) Hayat, F.; Demir, B.; Acarer, M.; Aslanlar, S.In this study, the effect of adhesive bonding on strength and strength-ductility behaviour of welding joint in electrical resistance spot welding of 7315 grade IF steel sheets was investigated. 7315 grade (DIN EN 10130-1999) IF steels were adhesively bonded and different welding current and welding cycle conditions were performed in welding process. For adhesive bonding, Loctite Terostat 9120-Grey and Terostat 9220-Black grade adhesive bonders were used. Additionally, adhesively bonded joint samples were also performed without welding. Microstructure and tensile-shear tests of the adhesively bonded and welded materials were evaluated. Failure modes of the weld bonded tensile sheared samples were observed to be different from only welded samples. Experimental results have shown that with the increase in the weld time and weld current, the effect of the adhesive weld bonding on tensile performance also increases.Öğe Comparing Properties of Adhesive Bonding, Resistance Spot Welding, and Adhesive Weld Bonding of Coated and Uncoated DP 600 Steel(2011) Hayat, F.Zinc coated dual phase 600 steel (DP 600 grade) was investigated, utilisation of which has gradually increased with each passing day in the automotive industry. The adhesive bonding (AB), resistance spot welding (RSW), and adhesive weld bonding (AWB) joints of the zinc coated DP 600 steel were investigated. Additionally, the zinc coating was removed using HCL acid in order to investigate the effect of the coating. The microstructure, tensile shear strengths, and fracture properties of adhesive bonding (AB), resistance spot welding (RSW), and adhesive weld bonding (AWB) joints of the coated and uncoated DP 600 steel were compared. In addition, a mechanical-electrical-thermal coupled model in a finite element analysis environment was utilised. The thermal profile phenomenon was calculated by simulating this process. The results of the tensile shear test indicated that the tensile load bearing capacity (TLBC) values of the coated specimens among the three welding methods were higher than those of the uncoated specimens. Additionally, the tensile strength of the AWB joints of the coated and uncoated specimens was higher than that of the AB and RSW joints. It was determined that the fracture behaviours and the deformation caused were different for the three welding methods. © 2011 Central Iron and Steel Research Institute.Öğe Effect of Aging Treatment on Surface Roughness, Mechanical Properties, and Fracture Behavior of 6XXX and 7XXX Aluminum Alloys(Springer, 2014) Sevim, I.; Sahin, S.; Cug, H.; Cevik, E.; Hayat, F.; Karali, M.The effect of aging treatment on the surface roughness and mechanical properties of AA6061 and AA7075 alloys was studied. Microhardness and tensile tests were used to investigae the mechanical properties. X-ray diffraction analysis was used to investigate the surface of the specimens. Furthermore, after tensile tests fractured surfaces were examined with scanning electron microscopy. An atomic force microscope was employed for analysis of the effect of aging treatment on surface roughness. Higher surface roughness with an increase in the volume fraction of the precipitate was revealed.Öğe Effect of aging treatment on the microstructure and mechanical properties of the similar and dissimilar 6061-T6/7075-T651 RSW joints(Elsevier Ltd, 2012) Hayat, F.The similar and dissimilar resistance spot weldability of 6061-T6 and 7075-T651 aluminium alloys was investigated in this study. Resistance spot weldability of commercial and aged samples in different variations was examined. The microstructure, microhardness, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron probe micro-analyses (EPMA) were conducted to study the effects aging heat treatment had on similar and dissimilar resistance spot welded (RSW) joints. In addition, tensile shear tests were performed to determine the mechanical properties and fracture behaviour of welded joints. The tests concluded that pre-weld aging heat treatment improves mechanical properties. © 2012 Elsevier B.V.Öğe Effect of heat treatment on microstructure, mechanical properties and fracture behaviour of ship and dual phase steels(2011) Hayat, F.; Uzun, H.Grade A (GA) and high strength steel DH36 ship steels possessing different chemical compositions were used, and strength properties of GA steel and DH36 steel were compared. Additionally, 4 types of dual phase (DP) steels with different martensite volume fractions (MVFs) were produced from GA steel by means of heat treatment and they were compared with other steels through conducting microstructure, microhardness, tensile and impact tests. The fracture surfaces of specimens (DH36, GA and DP steels) exposed to tensile and Charpy impact tests were investigated by scanning electron microscope. Furthermore, it was found that the specimens quenched from 800 and 900 °C had better strength than DH36 steel. The tensile test results indicated that the tensile strength of DP steel water quenched from 900 °C was 3 times that of GA steel and twice that of DH36 steel. © 2011 Central Iron and Steel Research Institute.Öğe Effect of weld time and weld current on the mechanical properties of resistance spot welded IF (DIN EN 10130-1999) steel(Redakcia Kovove Materialy, 2009) Hayat, F.; Demir, B.; Acarer, M.; Aslanlar, S.In this study, the effects of weld current and weld time on the tensile peel strength and tensile-shear strength of 7114 grade IF (Interstitial Free) steel sheets joined by spot welding were investigated. Weld processes were performed by using 3, 5, 7, 9 kA weld current and 5, 10, 15, 20, 25, 30 weld cycles. The microstructure of the welded materials was evaluated. The hardness profiles were also determined. Experimental results showed that tensile shear loading bearing capacity and hardness of both weld and heat affected zones increased for increasing weld time and weld current. Weld nugget diameter extended by increasing weld time or/and weld current, so tensile shear load bearing capacity and tensile peel strength increased. Tensile fracture behaviour of the samples was evaluated. Weld lobe was constructed with respect to weld current and time.Öğe Effect of weld time and weld current on the mechanical properties of resistance spot welded IF (din en 10130-1999) steel(2009) Hayat, F.; Demir, B.; Acarer, M.; Aslanlar, S.In this study, the effects of weld current and weld time on the tensile peel strength and tensile-shear strength of 7114 grade IF (Interstitial Free) steel sheets joined by spot welding were investigated. Weld processes were performed by using 3, 5, 7, 9 kA weld current and 5, 10, 15, 20, 25, 30 weld cycles. The microstructure of the welded materials was evaluated. The hardness profiles were also determined. Experimental results showed that tensile shear loading bearing capacity and hardness of both weld and heat affected zones increased for increasing weld time and weld current. Weld nugget diameter extended by increasing weld time or/and weld current, so tensile shear load bearing capacity and tensile peel strength increased. Tensile fracture behaviour of the samples was evaluated. Weld lobe was constructed with respect to weld current and time.Öğe The influence of the heat treatment on mechanical and microstructure properties of Fe-Mn-C high-manganese steel(Redakcia Kovove Materialy, 2016) Akinay, Y.; Hayat, F.The influence of the heat treatment on mechanical properties and microstructures of the Fe-22Mn-0.6C high-manganese steel was investigated at different annealing temperatures. A high-Mn TWIP (Twinning Induced Plasticity) steel specimens (0.6C, 24Mn steel) were fabricated, and were annealed at 700, 900, and 1100 degrees C for 150 min and then air-cooled. The carbide precipitates in the microstructure of specimens were annealed at 700 degrees C. However, the microstructure of specimens annealed at 900 and 1100 degrees C is austenite and some grains include annealing and mechanical twins. The results show that tensile strength of the material decreased, and the ductility of material was improved with increasing annealing temperature. Besides that, hardness value decreased between 700 and 1100 degrees C, which shows a good agreement with the equilibrium dissolution temperature of M3C carbides.Öğe The influence of the heat treatment on mechanical and microstructure properties of Fe-Mn-C high-manganese steel(Slovenska Akademia Vied, 2016) Akinay, Y.; Hayat, F.The influence of the heat treatment on mechanical properties and microstructures of the Fe-22Mn-0.6C high-manganese steel was investigated at different annealing temperatures. A high-Mn TWIP (Twinning Induced Plasticity) steel specimens (0.6C, 24Mn steel) were fabricated, and were annealed at 700, 900 and 1100 C for 150 min and then air-cooled. The carbide precipitates in the microstructure of specimens were annealed at 700 C. However, the microstructure of specimens annealed at 900 and 1100°C is austenite and some grains include annealing and mechanical twins. The results show that tensile strength of the material decreased, and the ductility of material was improved with increasing annealing temperature. Besides that, hardness value decreased between 700 and 1100 C, which shows a good agreement with the equilibrium dissolution temperature of M3C carbides.Öğe Investigation of corrosion behaviour of boronised cold rolled high manganese steel(Inderscience Publishers, 2023) Sezgin, C.T.; Hayat, F.Corrosion behaviour of boronised high manganese steels (HMS) was investigated in this study. Pack-boronising was processed at 950°C, 900°C and 850°C for 2 h, 4 h, and 6 h. Boride layers of HMS unpredictably exhibited saw-tooth morphology. FeB, Fe2B, MnB and SiC phases were determined by XRD analyses. The increase in boronising temperature and time caused an increase in boride layer thickness. Although the corrosion rates were lower in boriding processes at 850°C, the corrosion rate of most of the samples boronised at 900 and 950°C was higher than the un-boronised HMS due to micro-cracks and pores formed in the boride layers. Copyright © 2023 Inderscience Enterprises Ltd.Öğe The investigation of the use of trip steels in automotive industry(2010) Hayat, F.Turkey has started the integrated steel production with the foundation of Karabük Iron-Steel Factory which is the first heavy industry attempt of the country. Even though Turkish Iron-Steel industry has been exposed to various crises until the 21st century, it took an important step into a growth process starting from the year 2001. However, to keep up with the sectoral changes developing in the global economy and to direct the production in accordance with such developments have become a requirement. For this purpose, it might be an important objective to produce steel for the automotive industry that has come into prominence in our country with a high level of added value and income. Production of light and advanced high-strength steel for Turkish and World industries is a very critical technology. In developed countries, the steel industry is based on integrated plants and has been directed to products such as advanced high-strength steel, stainless steel, etc. that have a very high added value. In spite of that different kinds of steel sheet are being produced in our country, the dual phase steel which has been intensively utilized especially in recent years is being produced in low quantities whereas TRIP steel, which shall be used more with the purpose of reducing the weight of the vehicles in future, is not being produced. The literature study has done considering most recent research shaped within the frame of original studies conducted in recent years. In this study, TRIP steels have been introduced in comparison with other steels used in automobiles based on certain criteria such as microstructure, tensile strength, crash (impact), formability and fatigue. Furthermore, a study has also been conducted about the utilization of the TRIP steel in automotive industry and manufacturability in Turkey.Öğe Nucleus geometry and mechanical properties of resistance spot welded coated-uncoated DP automotive steels(2013) Sevim, I.; Hayat, F.; Kulekci, M.K.In this study, mechanical properties of resistance spot welding of DP450 and DP600, galvanized and ungalvanized automotive sheets have been investigated. The specimens have been joined by resistance spot welding at different weld currents and times. Welded specimens have been examined for their mechanical, macrostructure and microstructure properties. Depending on the weld current and time, effects of zinc coating on tensile properties, microhardness values as well as microstructure nugget geometry and nucleus size ratio have been investigated. X-ray diffraction analysis has been used to investigate the phase that formed at the joint interface. Result of the experiment show that nugget diameter, indentation depth and tensile load-bearing capacity are affected by weld parameters. Coating prevents full joining at low parameters. Microhardness increased in heat-affected zone and weld metal. © 2013 Indian Academy of Sciences.Öğe Tensile shear stress and microstructure of low-carbon dual-phase Mn-Ni steels after spot resistance welding(Springer, 2007) Hayat, F.; Demir, B.; Acarer, M.Tensile shear stresses and microstructure of dual steels with different volume fractions of martensite are studied after spot resistance welding. A Mn-Ni low-carbon steel heated in the intercritical temperature range and cooled in water and in air is studied. Spot resistance welding of test pieces is performed for different times at constant welding pressure and peak value of the welding current. The microstructure of the welded specimens is investigated and their permissible tensile shear stresses are determined.
