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    Öğe
    An Investigation of Production and Properties of RHA Reinforced Hybrid Composites by Vacuum Infiltration Method
    (Kırıkkale Üniversitesi, 2021) Tanış, Naci Arda; Okur, Onur; Duran, Osman; Yılmaz, Erkan; Türkmen, Mustafa; Mohamed Ariff, Azmah Hanim; Dele-afolabi, Temitope
    The harmful effect of agricultural waste has been intensified over the last decade and impacts the environment every passing day. Rice husk waste is a major problem in Turkey and the far east countries. Due to the economic dependence of the mass cultivation and the production of rice, the disposal of the waste appears both time and money consuming. Alternative methods sought over the years and the implementation of the rice husk in the production of composites is seen as a promising method. RHA is a burning residue of rice husk and the implementation of RHA in the production of aluminum composites gained attention in recent years. In this study, aluminum composites having 5 wt.% Al2O3 reinforcement and 5 wt.% Al2O3/0.5, 1.0, and 1.5 wt.% RHA reinforcement were produced by vacuum infiltration process which is a cheap and cost-effective route. AA7075 alloy without any reinforcement was produced for comparison. Solution heat treatment at 480 °C for 2 hours was applied and then quenched following by aging heat treatment at 120 °C for 8 hours. The microstructure, microhardness, and wear tests of all composites were investigated. Increasing RHA content up to 1 wt.% and aging heat treatment increased the hardness of composites. Abrasion coefficient decreased by increasing RHA content.
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    Chemical Composition Optimization and Isothermal Transformation of ?-Transformation-Induced Plasticity Steel for the Third-Generation Advanced High-Strength Steel Grade
    (Wiley-V C H Verlag Gmbh, 2024) Okur, Onur; Davut, Kemal; Palumbo, Gianfranco; Nalcaci, Burak; Guglielmi, Pasquale; Yalcin, Mustafa Alp; Calin, Recep
    A new low-manganese transformation-induced plasticity steel is designed with optimized nickel content to achieve superior strength and ductility while minimizing the use of expensive nickel. The steel is optimized using JMatPro software, then cast, and hot rolled. To assess the effect of intercritical annealing on austenite (martensite at room temperature) volume fraction and carbon content, hot-rolled steel samples quenched from different annealing temperatures (680-1100 degrees C) are used. Additionally, hot-rolled steel coupons are intercritically annealed at about 50% austenite formation temperature (740 degrees C) and then subjected to isothermal treatments at 300-425 degrees C for varying times (10-90 min). After optimizing these treatments to maximize retained austenite (RA), tensile specimens are heat-treated first at 740 degrees C and then isothermally at 325 degrees C. Thermodynamic calculations suggest that aluminum combined with silicon may lead to the delta ferrite formation, and even minimal nickel content can stabilize a considerable amount of austenite. In the experimental studies, it is shown that lower-temperature bainitic holding enhances austenite stability by enriching the carbon content. Optimized two-stage heat treatments yield up to 25.8% RA, with a tensile strength of 867.2 MPa and elongation of 40.6%, achieving a strength-elongation product of 35.2 GPax%, surpassing the third-generation advanced high-strength steel grades minimum requirement of 30 GPax%.
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    Öğe
    Correction: Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron (International Journal of Metalcasting, (2022), 16, 4, (1836-1848), 10.1007/s40962-021-00723-3)
    (Springer Science and Business Media Deutschland GmbH, 2023) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, Mehmet
    The original online version of this article was revised. The graphical abstract, Fig. 8, Table 4, and miscellaneous values throughout the text were corrected. © 2023, American Foundry Society.
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    Öğe
    Dönüşüm Kaynaklı Plastisite (TRIP) ve Üçüncü Nesil İleri Yüksek Mukavemetli Çelikler Üzerine Bir İnceleme
    (Kırıkkale Üniversitesi, 2023) Okur, Onur; Erdoğan, Mehmet
    Elektrikli araçların kullanımı artarken araçların ağırlığının azaltılması ise yakıt tasarrufu için elzemdir. Bu ise sacların kesit kalınlığının azaltılması ile mümkündür. Araç ağırlığının yaklaşık %70’ini demir esaslı malzemeler oluşturduğundan bu yolla büyük oranda ağırlık tasarrufu yapılabilmektedir. İnce sacların çarpışma anında yeterince koruyamama riski vardır. Bu yüzden araştırmalar hem yüksek mukavemet hem de şekillendirilebilirlik dengesi sunan İleri Yüksek Mukavemetli Çelikler (İYMÇ) üzerinde yoğunlaşmıştır. Özellikle, 3. Nesil İYMÇ’ler araştırmacıların ilgisini çekmektedir. Bunlar birinci nesilden daha yüksek mekanik özellikler vadederken, 2. Nesile kıyasla ucuzdurlar. 3. Nesil İYMÇ’ler genellikle çok fazlı mikroyapıya sahiptir ve fazların mikroyapıda bulundukları oranda çeliğin özelliklerini etkilemektedirler. Böylece farklı özelliklere sahip fazların sinerjetik etkisi ile çeliğin özellikleri istenildiği gibi ayarlanabilmektedir. Bu fazların içerisinde kalıntı östenit (KÖ) fazı, bu fazın miktarı ve kararlılığı önemlidir. Yüksek miktarda ve iyi kararlılığa sahip KÖ, deformasyon ile aşama aşama martensite dönüşerek plastik kararsızlığı yüksek gerinim bölgelerine ötelemekte ve çeliğin hasara uğramasını geciktirmektedir. Bu mekanizma TRIP etkisi olarak adlandırılmaktadır. Bu durum çeliklerin yüksek mekanik özelliklere sahip olmasının başlıca sebebidir. Yapılan bu inceleme ile TRIP mekanizması, dönüşüm kinetiği ve KÖ kararlılığını etkileyen faktörler incelenmiştir. 3. Nesil İYMÇ’lerinden Su Verme ve Paylaştırma Çelikleri, Orta Mn’lı Çelikler ve Karbürsüz Beynitik Çelikler irdelenerek termomekanik ve ısıl işlem süreçlerinin mikroyapıya etkisi açıklanmıştır.
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    Öğe
    Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron
    (Springer Science and Business Media Deutschland GmbH, 2022) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, Mehmet
    The present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu–Ni–Mo-alloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 °C for the duration of 15–30–60 min followed by holding in a salt bath at an austempering temperature of 260 °C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. Graphical Abstract: [Figure not available: see fulltext.] © 2021, American Foundry Society.
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    EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON
    (Springer Int Publ Ag, 2022) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat
    The present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu-Ni-Moalloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 degrees C for the duration of 15-30-60 min followed by holding in a salt bath at an austempering temperature of 260 degrees C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. [GRAPHICS] .
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    EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON (vol 16, pg 1836, 2021)
    (Springer Int Publ Ag, 2023) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat
    [Abstract No tAvailable]
  • Küçük Resim
    Öğe
    An Investigation on the Microstructure and Wear Properties of TiB2 Reinforced AA2014 Aluminium Alloy Produced by Vacuum Infiltration
    (Walter De Gruyter Gmbh, 2015) Araz, Sule Ocak; Çalın, Recep; Pul, Muharrem; Bican, Osman; Okur, Onur
    In this study, microstructural, mechanical and wear properties of TiB2 reinforced Al 2014-based composites produced by vacuum infiltration were investigated under different production temperatures. It was observed that the microstructures of the composites consisted of Al matrix and TiB2 particles. TiB2 particles exhibit various shapes such as cubic, triangle and spherical. It was observed that the hardness and porosity of the composites increased with increasing TiB2 content. It was also observed that the production temperature has an important effect on the porosity and hardness of the produced composites. The highest wear resistance was obtained from Al 2014-8% TiB2 composite among the materials tested. It was observed that the production temperature and hardness are effective parameters on wear of produced composites. Evaluation of microstructural and mechanical test results suggest that it would be beneficial to keep the production temperature around 800 degrees C and Al 2014-8% TiB2 composite can be recommended for engineering applications where the hardness and wear resistance are considered to be significant factors.
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    INVESTIGATION ON THE WEAR BEHAVIOUR AND PROPERTIES OF RHA REINFORCED 7075 ALUMINIUM T6 COMPOSITES PRODUCED BY VACUUM INFILTRATION
    (Microscopy Society of Malaysia, 2022) Tanis, Naci Arda; Okur, Onur; Jafaar, Che Nor Aiza; Ariff, Azmah Hanim Mohamed; Çalin, Recep
    Aluminum matrix composites containing hard ceramic particles have higher strength, hardness and wear resistance than conventional materials. However, the high cost of hard ceramic reinforcements has led researchers to obtain ceramic reinforcement from organic wastes such as rice husk and eggshell, and they are looking for ways to increase the hardness and wear properties by reinforced these organic wastes. In this study, 1, 2, and 4 vol.% rice husk ash (RHA) were added to AA7075 metal matrix. Samples were produced in a steel tube under 550 mmHg vacuum at 750 °C for 3 minutes. T6 heat treatment (aging) was applied to the samples. The density, porosity, and hardness of non-aged and aged samples were measured and compared. In addition, SEM and EDS analysis of aged samples were performed and wear properties under 20 N load was investigated. While the hardness and the porosity of T6 heat treated composites increased with increasing reinforcement volume ratio, T6 heat treatment did not improve the hardness and the wear properties of the composites significantly compared to unreinforced (0 vol%) sample. Wear tests showed that the mass loss increased with the increment of reinforcement-volume ratio. Increasing RHA content resulted in worsening the wear behavior of composites because of the poor wettability of RHA particles. © 2022, Microscopy Society of Malaysia. All rights reserved.