Yazar "Turkmen, Mustafa" seçeneğine göre listele

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    Bake-Hardening Response of High Martensite Dual-Phase Steel with Different Morphologies and Volume Fractions
    (Chinese Acad Sciences, Inst Metal Research, 2014) Turkmen, Mustafa; Gunduz, Suleyman
    Bake-hardening behaviour of carbon steel with different martensite morphologies and volume fraction was investigated. The specimens with fibrous and bulky martensite were prestrained in tension by 4%. After this, they were unloaded and bake hardened at 180 degrees C for 10-160 mm. It was found that dual-phase steel samples which were bake hardened at 180 degrees C for 20 min showed an increase in the yield stress (YS) and ultimate tensile stress (UTS) but a decrease in ductility. Further increase in the bake-hardening time of 80 or 160 min has reduced the YS and UTS, but increased the ductility. Delta sigma (increase in stress due to bake hardening), YS and UTS values are higher for the microstructure containing fibrous martensite compared to the microstructure-containing bulky martensite. It was also observed that at a given baking temperature Delta sigma, YS and UTS increased by volume of martensite.
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    THE EFFECT OF COOLING RATE ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al-Mg-Si (6063) ALLOY
    (Pamukkale Univ, 2015) Turkmen, Mustafa; Akdemir, Auzhan; Taspinar, Yusuf; Yildiz, Murat; Gunduz, Silleyman
    In this study, the effect of cooling rate on microstructure and mechanical properties of Al-Mg-Si (6063) alloys was investigated. In order to obtain different cooling rate, samples heat treated at 520 degrees C for 2 h and then cooled in furnace, sand, air, oil and water environments. A decrease in the cooling rate caused the growth of grains and precipitates as the strength of Al-Mg-Si alloys reduced. As a result, Al-Mg-Si alloy was found to change significantly the properties of strength and forming depending on the cooling conditions.
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    Effect of Different Current Values on Microstructure and Mechanical Properties of Microalloyed Steels Joined by the Submerged Arc Welding Method
    (Mdpi Ag, 2016) Karabulut, Hasan; Turkmen, Mustafa; Erden, Mehmet Akif; Gunduz, Suleyman
    In this study, microalloyed steels were joined by using the submerged arc welding method at different welding currents of 350 A, 400 A and 450 A. The effects of selected welding parameters on the microstructure and mechanical properties of welded materials were investigated. Tensile tests and microhardness measurements were performed. Microstructural changes have been identified in the welding zone. The results showed an increase in hardness and tensile strength depending on the current intensity. The heat affected zone was observed much wider with the increase in welding current.
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    THE EFFECT OF MARTENSITE MORPHOLOGY ON STATIC STRAIN AGEING BEHAVIOUR OF DUAL PHASE STEELS
    (Gazi Univ, Fac Engineering Architecture, 2013) Turkmen, Mustafa; Gunduz, Suleyman
    In this study, strain ageing behaviour of dual phase steel with different martensite morphology was investigated. Three different types (Intercritical annealing, intermediate quenching and step quenching) of heat treatment was applied in the critical temperature (775 degrees C). Ageing experiments after 4 % prestrain were carried out at 180 degrees C for different times ranging from 10 to 160 min. The microstructure after different heat treatments applied to the work pieces with the network, fiber, and the bulky martesite morphologies have been identified. It was found that the martensite morphology has no effect on the trend of Delta Y (an increase in strength due to strain ageing), YS and UTS at different ageing times for 180 degrees C. However, at a given ageing time for 180 degrees C Delta Y, YS, UTS and hardness values of fibrous martensite are higher than network or bulky martensite.
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    The Effect of Mechanical Properties and the Cutting Parameters on Machinability of AISI 5140 Steel Cooled at High Cooling Rates After Hot Forging
    (Gazi Univ, 2019) Ozlu, Baris; Demir, Halil; Turkmen, Mustafa
    In this study, the effect of mechanical properties and cutting parameters (Cp) on the machinability of AISI 5140 steel cooled at high cooling rates after hot forging was investigated. The microstructural examinations and hardness measurements of the as-received AISI 5140 steel and the workpieces cooled in the oil and polymerized water after hot forging were performed. Turning process was conducted by using a coated ceramic tool at five different cutting speeds (Vc) (120, 150, 180, 210, and 240 m/min), four different feed rates (fn) (0.04, 0.08, 0.12, and 0.16 mm/rev), and four different depths of cut (ap) (0.4, 0.6, 0.8, and 1 mm) under dry machining conditions. SEM examinations of the cutting tools were also performed. It was seen from the results that the changing microstructure and hardness values had a significant effect on cutting forces (Fc) and surface roughness (Ra) from the Cp depending on cooling rate. While the highest Fc were reached in the workpiece with the highest hardness cooled in the polymerized water after hot forging, the lowest surface roughness (Ra) was obtained in the same workpiece.
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    The Effect of Mn and Ti Ratio on Microstructure and Mechanical and Machinability Properties of 316 L Stainless Steel Used in Biomedical Applications
    (Mdpi, 2023) Turkmen, Mustafa; Tanouz, Alla Muhammed; Akgun, Mahir; Erden, Mehmet Akif
    In this study, titanium (Ti) and manganese (Mn) element powders in determined amounts (0.35-0.75 and 1.5 wt %) were added into the 316 L stainless steel matrix by means of powder metallurgy (PM) technology, either individually or in pairs, and the desired composition was obtained as a powder mixture. The powders used in the study were cold-pressed tensile sample molds prepared in ASTM E8M standards, unidirectionally cold-pressed under 750 MPa compression pressure and formed into blocks. After pressing, the raw strength samples were sintered in an atmosphere-controlled tube furnace at 1250 degrees C for two hours in an argon atmosphere. The microstructure and mechanical properties of the produced PM steels were characterized using an optical microscope, SEM, EDS, tensile test, and hardness test. The results showed that the stainless steel samples with 0.35 (Ti and Mn) added to 316 L stainless steel had the highest yield strength, tensile strengths, and hardness strengths. However, with the addition of 0.75-1.5 Ti, 0.75-1.5 Mn and 0.75-1.5 (Ti and Mn) to 316 L stainless steel, a decrease was observed in the mechanical properties. Moreover, the stainless steel sample with 0.35 (Ti and Mn) added to 316 L stainless steel is better than other samples in terms of surface quality.
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    Effect of niobium addition on the microstructure and wear properties of mechanical alloyed Cu-Al-Ni shape memory alloy
    (Walter De Gruyter Gmbh, 2024) Yavuzer, Bekir; Turkmen, Mustafa; Bicakci, Unal; Ozyurek, Dursun
    In this study, the influence of the addition of Nb in varying amounts (0.5, 1, 1.5, and 2 wt.%) to Cu-14Al-4Ni shape memory alloy on the microstructure and wear behavior of the alloy was investigated. Cu-Al-Ni-xNb alloys were produced from elemental powders using the mechanical alloying (MA) method. The microstructures of the produced samples were examined using SEM + EDS and XRD, and density and hardness measurements were performed. For the wear tests of Cu-14Al-4Ni and alloys containing different amounts of Nb, a pin-on-disk type wear testing device was used with three different loads (10 N, 20 N, and 30 N) and five different sliding distances (400 m, 800 m, 1,200 m, 1,600 m, and 2000 m). As a result of the conducted research, it was determined that an increase in the Nb content resulted in a decrease in the average grain size and a more homogeneous grain size distribution. The highest hardness and density values were measured in the alloy with 2 wt.% Nb addition. In the wear tests, it was observed that the friction coefficients decreased with increasing load, and the lowest wear rate was achieved in the alloy with 2 wt.% Nb addition.
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    EFFECT OF THE ADDITION OF NIOBIUM AND ALUMINIUM ON THE MICROSTRUCTURES AND MECHANICAL PROPERTIES OF MICRO-ALLOYED PM STEELS
    (Inst Za Kovinske Materiale I In Tehnologie, 2016) Gunduz, Suleyman; Erden, Mehmet Akif; Karabulut, Hasan; Turkmen, Mustafa
    In this work, the effects of the addition of Nb and Al on the microstructures and tensile behaviours of micro-alloyed powder metallurgy (PM) steels were investigated. The microstructure of the micro-alloyed PM steels was examined by light microscope, SEM, XRD, XRF and EDS. The results indicated that the addition of (0.1, 0.15 or 0.2) % of Nb-Al increases the yield strength (YS) and the ultimate tensile strength (UTS) of the PM sintered steels. Elongation also tends to improve with an increasing Nb and Al content. In addition, the Nb and Al limit the grain growth during austenitization.
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    Effect of vanadium addition on the microstructure and mechanical properties of low carbon micro-alloyed powder metallurgy steels
    (Carl Hanser Verlag, 2016) Erden, Mehmet Akif; Gunduz, Suleyman; Karabulut, Hasan; Karabuk; Turkmen, Mustafa
    In the present experimental work, the effects of vanadium additions on the microstructures and mechanical properties of powder metallurgy (PM) steel and microalloyed powder metallurgy (PM) steels were investigated. The microstructures of the PM steel and microalloyed PM steels were characterized by optic microscope, SEM and EDS. Experimental results showed that vanadium microalloyed steels can be produced by PM technology. The addition of vanadium limits grain growth during austenitization prior to air cooling and increases the strength in the sintered conditions. By limiting austenite grain growth, the precipitates result in significant improvement in strength.
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    Influence of ageing treatment on microstructure, mechanical properties and adhesive wear behaviour of 6063 aluminium alloy
    (Emerald Group Publishing Limited, 2014) Buyukdogan, Serkan; Gunduz, Suleyman; Turkmen, Mustafa
    Purpose - The paper aims to provide new observations about static strain ageing in aluminium (Al) alloys which are widely used in structural applications. Design/methodology/approach - The present work aims to provide theoretical and practical information to industries or researchers who may be interested in the effect of static strain ageing on mechanical properties of Al alloys. The data are sorted into the following sections: introduction, materials and experimental procedure, results and discussion and conclusions. Findings - Tensile strength, proof strength (0.2 per cent) and percentage elongation measurement were used to investigate the effect of strain ageing on the mechanical properties. Wear tests were performed by sliding the pin specimens, which were prepared from as-received, solution heat-treated, deformed and undeformed specimens after ageing, on high-speed tool steel (64 HRC). It is concluded that the variations in ageing time improved the strength and wear resistance of the 6063 Al alloy; however, a plastically deformed solution-treated alloy has higher strength and wear resistance than undeformed specimens for different ageing times at 180 degrees C. Practical implications - A very useful source of information for industries using or planning to produce Al alloys. Originality/value - This paper fulfils an identified resource need and offers practical help to the industries.
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    INVESTIGATION OF MACHINABILITY OF COOLED MICROALLOY STELL IN OIL AFTER THE HOT FORGING WITH COATED AND UNCOATED CBN CUTTING TOOLS
    (Yildiz Technical Univ, 2018) Ozlu, Barn; Demir, Halil; Turkmen, Mustafa; Gunduz, Suleyman
    The aim of this study was to investigate the cutting forces and surface roughness of 38MnVS6 microalloyed steel quenched in oil following hot forging. The machinability tests were carried out by turning under dry cutting conditions using coated and uncoated cubic boron nitride (CBN) cutting tools at five different cutting speeds (120, 150, 180, 210 and 240 m / min), a constant feed rate (0.04 mm / rev) and a constant chip depth (0.6 mm). The microalloyed steel used in the experimental study was optically examined and a hardness test was applied. Scanning electron microscopy (SEM) was used to evaluate the wear on the cutting tools. The findings for the 38MnVS6 steel which was oil quenched after forging showed that due to the high cooling rate, a martensite structure had been formed and the hardness value was high. The lowest surface roughness values of 0.367 mu m and 0.164 mu m were obtained at a cutting speed of 180 m / min with the coated and the uncoated CBN cutting tools, respectively. In the turning experiments, the surface roughness values measured using the coated CBN cutting tool were about 103% higher than those measured using the uncoated CBN cutting tool and the highest cutting forces were obtained at a cutting speed of 120 m / min.
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    Investigation on the behaviour of medium carbon and vanadium microalloyed steels by hot forging test
    (Elsevier Sci Ltd, 2013) Kaynar, Ahmet; Gunduz, Suleyman; Turkmen, Mustafa
    Two medium carbon steel grades were used in the present investigation. One of them was microalloyed with vanadium. Both steel grades were subjected to a controlled closed die forging followed by cooling in sand, air or oil mediums. Final microstructures and mechanical properties were evaluated by optical microscopy, scanning electron microscopy, hardness and tensile tests. The results indicated that the microstructures of all close die forging and cooling conditions are dominated by ferrite and pearlite phases with different morphologies and grain sizes according to both chemical composition and cooling rate. Oil quenching leads to a formation of relatively fine ferrite and pearlite in medium carbon steel (MC) or martensite in medium carbon microalloyed steel (MC-MA). Relatively fine ferrite, pearlite and martensite increase strength but decrease ductility. The cooling rate has a remarkable effect on the microstructure and mechanical properties at room temperature. (c) 2013 Elsevier Ltd. All rights reserved.
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    Microstructural characterization and mechanical properties of microalloyed powder metallurgy steels
    (Elsevier Science Sa, 2014) Erden, Mehmet Akif; Gunduz, Suleyman; Turkmen, Mustafa; Karabulut, Hasan
    The effects of Ti additions on the microstructures and mechanical properties of microalloyed powder metallurgy (PM) steels were investigated. The microstructure of the microalloyed PM steels was characterized with the help of optic microscope, SEM and EDS. Experimental results showed that Ti microalloyed steels can be produced by PM technology. The addition of Ti increases the strength in the sintered conditions. In addition, Ti limits grain growth during austenitization prior to cooling. By limiting austenite grain growth, the precipitates result in significant improvement in strength. (C) 2014 Elsevier B.V. All rights reserved.
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    Microstructural Effects on Fatigue Behaviour of a Forged Medium Carbon Microalloyed Steel
    (Carl Hanser Verlag, 2013) Gunduz, Suleyman; Karabulut, Hasan; Erden, Mehmet Akif; Turkmen, Mustafa
    The effect of different microstructures on the fatigue behaviour of a medium carbon vanadium microalloyed steel has been studied. Specimens were subjected to a controlled closed die forging followed by cooling in sand, air or oil, respectively. The hardness and fatigue properties of the microalloyed steel are determined and compared with those of ferrite-pearlite and martensite microstructures obtained by cooling with different mediums after forging. Relatively fine ferrite and pearlite increase the fatigue strength of the steel, while the martensite structure reduces the fatigue strength. Characteristics of fatigue fracture surface morphology are summarized and related to fatigue crack initiation and propagation mechanisms in the forged medium carbon microalloyed steel. The cooling rate has a remarkable effect on the microstructure, hardness, and fatigue behaviour at room temperature.