hüseyin uzun - Academia.edu (original) (raw)

Papers by hüseyin uzun

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Jun 1, 2000

Demir-Bakir ve Demir-Bakir-Grafit karisunlari olmak uzere iki farkli demir esasli malzeme toz met... more Demir-Bakir ve Demir-Bakir-Grafit karisunlari olmak uzere iki farkli demir esasli malzeme toz metalurjisi yonteini ile uretilmistir. Uretim islemi ise, tozlarin karistirilmasi, soguk presleme, 1125°C' de ve parcalanmis amonyak atmosferi altinda sinterleme vefirinda sogunna kademelerini icermektedir. Demir Bakir karisimlarinda bakir yuzdeleri %2 'den, %3.5' a kadar 0.5 adimlarla arttirilmistir. Demir-Bakir-Grafit karisimlarinda ise, bakir miktari sabit (%3) tutulurken,grafit miktari %0'dan %1.25'e 0.25 adimlarla arttirilmistir.

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Apr 1, 2002

Ozet -Petrol ve dogal gaz boru hatlarında yaygın olarak kullanılan ve tandem tozaltı kaynak metod... more Ozet -Petrol ve dogal gaz boru hatlarında yaygın olarak kullanılan ve tandem tozaltı kaynak metodu ile birleştirilen API 5L X65 d u al fazlı çeliğin kırılma to lduğu tespit edilmiştir. Kırılma to lduğu, çentikli üç nokta kırılma tokluğu deneyi kullanılara k belirlenmiştir. Çentik, hem kaynak dikişinin ortasına hem de ısının tesiri altındaki bölgesi (IT AB) içerisinin içine gelecek şekilde açılarak deney uygulanmıştır. Her bir nurnuneye gerilim giderme tavlaması uygulanarak, kırılma tokluğu değerlerinin nasıl etkilendiği değerlendirilmiştir. Elde edilen sonuçlara göre, gerilim giderme tavı uygulanmamış ve uygulanmış numunelerde, kaynak dikişinin kırılma to ld uğu, IT AB bölgesinin kırılma to lduğundan daha yüksek çıkmıştır. Anahtar Kelimeler -API 5L X65 çeliğinin kırılma tokluğu, spira l dikişli borular, tandem tozaltı kaynağı.

International Journal of Materials Research, Jul 1, 2012

ABSTRACT The aim of this study is to demonstrate the transformation of grade-A steel into dual-ph... more ABSTRACT The aim of this study is to demonstrate the transformation of grade-A steel into dual-phase steel by heat treatment, and the joint performance of dual-phase steels welded by means of the gas metal arc welding process using both solid and flux-cored welding wires. Dual-phase steels with different contents of martensite were obtained by intercritical annealing in different temperature ranges of a grade-A shipbuilding steel, followed by water quenching. The experimental results revealed that the tensile strength of the dual-phase steels joined by solid wire is higher than that of the flux-cored wire joints. The microstructure of grade-A steel consists of ferrite and pearlite, while the dual-phase steels consist of ferrite and martensite. On the other hand, while the martensitic phase is especially encountered in the weld metal of the dual-phase steels joined with the solid wire, the ferrite phase is more common in the weld metal of the flux-cored wire joints.

International Journal of Materials Research, Jun 1, 2010

Journal of Iron and Steel Research International, Aug 1, 2011

The mechanical and corrosion properties of gas metal arc additive manufacturing (GMA-AM) 316L cou... more The mechanical and corrosion properties of gas metal arc additive manufacturing (GMA-AM) 316L could be optimized by modifying the volume fractions of sigma(σ) and delta-ferrite(δ) phases through heat treatment. Results show that the heat treatment at 1000°C to 1200°C for one hour will not obvious influence the morphology of grains in steel but largely influence the contents of σ and δ phases. The heat treatment at 1000°C effectively increases the amount of σ phase in steel, causing both increase of UTS and YS but decrease of El and RA. The heat treatment at 1100°C to 1200°C completely eliminates σ phase, leading to the decrease of UTS and YS but increase of El and RA. The σ phase has better strengthening effect than δ phase, but which may degrade ductility and increase the possibility for cracks generation in steel. Meanwhile, limiting the number of both σ and δ phases through heat treatment can improve the corrosion resistance of steel. And σ phase appears more detrimental impact on degradation the corrosion resistance of steel than δ phase.

DergiPark (Istanbul University), Feb 20, 2013

Bu calismada, yuksek hiz celiginden imal edilen takim kullanilarak surtunme karistirma kaynak yon... more Bu calismada, yuksek hiz celiginden imal edilen takim kullanilarak surtunme karistirma kaynak yontemiylebirlestirilen AA2124/SiCp/25 kompozit levhalarin karisim bolgesi icerisinde takim asinmasindan dolayiolusabilecek metal veya fazlarin varligi incelenmistir. Takim asinma kaybi uzerine dusuk ve yuksek takimilerleme hizinin (40 mm/dak ve 100 mm/dak.) etkisi arastirilmistir. Karisim bolgesinin analizi, SEM, BEI veXRD calismalari ile yapilmistir. Yapilan deneysel calismalar sonucunda, sabit takim donme hizinda takimilerleme hizinin 40 mm/dak.’dan 100 mm/dak.’ya arttirilmasiyla, karistirici ucun uc kisminda %10, kokkisminda ise %5’ lik bir asinma kaybi belirlenmistir. Ayrica karisim bolgesi icerisinde karistirici uctan kopmusmetal parcaciklari, SiO2 ve Cu2FeAl7 metallerarasi fazlarin var oldugu XRD analizi ile tespit edilmistir. Buetkenlere bagli olarak, kaynak performansi % 42 oraninda dusus gostermistir.

DergiPark (Istanbul University), Sep 1, 2006

Özet-Günümüz endüstrisinde, metallerin kaynağı oldukça yaygın olarak kullanılmaktadır. Bu sahada ... more Özet-Günümüz endüstrisinde, metallerin kaynağı oldukça yaygın olarak kullanılmaktadır. Bu sahada çalışanların dikkate alması gereken en önemli konulardan biri iş güvenliği ve kaynakçının

DergiPark (Istanbul University), Feb 19, 2013

Bu çalışmada, saf bakır (Cu) ve alüminyum (Al-1050) levhaların, 515 min-1 sabit takım devir hızın... more Bu çalışmada, saf bakır (Cu) ve alüminyum (Al-1050) levhaların, 515 min-1 sabit takım devir hızında ve farklı kaynak hızlarında sürtünme karıştırma kaynağıyla alın-alına birleştirilebilirlikleri incelenmiştir. En düşük kaynak hızında (12 mm min-1) başarılı bir Cu/Al-1050 birleştirmesi elde edilebilirken, kaynak hızının 30 ve 50 mm min-1 e artmasıyla oldukça zayıf birleştirmeler gerçekleşmiştir. Bu nedenle çalışmada, 12 mm min-1 kaynak hızındaki birleştirmenin mikroyapı karakterizasyonu yapılmış ve mekanik özellikleri değerlendirilmiştir. Bu birleştirmede optik ve taramalı elektron mikroskobunda mikroyapı incelemeleri ile enerji dağılımlı X-ışınları spektroskopisi (EDS), X-ışınları difraksiyonu (XRD), çekme testi ve mikrosertlik ölçümleri gerçekleştirilmiştir. Mikroyapı incelemeleri ve EDS analizleri, karışım bölgesinin alüminyumca zengin ve bakırca zengin yapıları içerdiğini göstermiştir. Kaynak bölgesinin XRD incelemelerinde, AlCu, Al 2 Cu 3 , AlCu 4 ve Al 4 Cu 9 metaller arası bileşiklerin varlığı tespit edilmiştir. İmaj analiz programıyla bakırca zengin fazların karışım bölgesindeki hacimsel oranının yaklaşık %32 olduğu hesaplanmıştır. Çekme testi sonuçları, Cu/Al-1050 birleştirmesinin çekme mukavemetinin Cu ana metalinkinden %50, Al-1050 ana metalinkinden ise %24 düşük olduğunu göstermiştir. Mikrosertlik ölçümlerinde ise, karışım bölgesindeki sertliklerin ana metallere göre arttığı ve 74-280 HV arasında değiştiği görülmüştür.

Periodicals of Engineering and Natural Sciences (PEN), Oct 3, 2013

The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase... more The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase steel by heattreatment at the chosen 730°C and 800°C intercritical temperature for 60 min followed by cold water quenching. The second aim of this study is to investigate the mechanical properties and the corrosion behaviours in 3.5% NaCl solution of Grade-A and dual-phase steels welded by flux-cored arc welding (FCAW). It was carried out the mass loss measurements and investigated the micro and macrostructures of welding zone using by optical microscope. The present study has demonstrated that Grade-A ship steel consisting of ferrite and pearlite can be successfully transformed to the dual-phase steel at the chosen intercritical temperatures. The microstructure of transformed dualphase steel consists of island of martensite in a ferrite matrix. The Grade-A and transformed dual-phase steels were successfully joined by FCAW. The mechanical results showed that the tensile strength of the transformed dual-phase steel were higher, but lower elongation than that of the Grade-A steel. The results from the immersion test in 3.5% NaCl solution showed that the corrosion behaviours of the dual-phase and Grade-A steels depend upon the morphology of the phase constituents. The corrosion rate of the transformed dual-phase steel with ferrite-martensite structure was lower than that of the Grade-A steel with ferrit-pearlite structure. The corrosion has preferential started at fusion line and progressed towards the heat affected zone (HAZ) of the welded dual-phase and Grade-A steels.

Key Engineering Materials, May 1, 2004

The joining of functionally graded materials (FGMs) based on Al-2124/SiC(p) composite system to i... more The joining of functionally graded materials (FGMs) based on Al-2124/SiC(p) composite system to itself was carried out using a rotary friction welding technique. Mechanical powder metallurgy processing involving cold pressing and hot extrusion has been used to fabricate bulk functionally graded composites (FGCs) with single radial graded core. The central core of the single-core FGC was unreinforced Al-2124 alloy which was surrounded by a SiC reinforced surface layer. The influence of friction and forging pressures on the plastic deformation zone of single-core FGCs near the weld interface was investigated. The effect of unreinforced central core in the singlecore FGC on the plastic deformation and hardness of the welding zone were also reported. The results show that friction welding could be used to the joining of single-core functionally graded composites. Three different zones of the microstructure in the welding zone, namely Zud, Zpd and Zpl are observed. A SiC reinforced layer in the Zpl region was also observed. The width of welding zone is decreased with increasing the forging pressure.

At this work, it was aimed that to overcome the prejudice of society about Vocational and Technic... more At this work, it was aimed that to overcome the prejudice of society about Vocational and Technical Education (VET); to improve effective thinking methods and skills for VET by societies; to improve some suggestions to build cooperation between VET, labor market and employee for critical and analytical thinking way. The aim of this study is to determine the evaluation of what kind of methods needs to educate the students in Vocational and Technical Education (VET) according to what labor market needs; what kind of employee skills labor market requests; what VET schools make to educate the high skills employee; why the high practical skill employee requesting from labor market not to educate by VET; why the high practical skill employee frequently done the workplace switching; how young people encourage to go VET. For these purposes, it was organised Sakarya first vocational education workshop by the cooperation of Sakarya provincial directorate of National Education and East Marmara...

International Journal of Materials Research, 2010

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Jun 1, 2000

Fonksiyonel kademeli degisken malzemeler yeni bir kompozit malzeine turu dur. Bu malzemeler, bir ... more Fonksiyonel kademeli degisken malzemeler yeni bir kompozit malzeine turu dur. Bu malzemeler, bir makine parcasinin belirli bolgelerinde istenilen bir ozelligi elde etmek icin dizayn edilmis olup, malzeinenin kimyasal birlesimi, mikroyapisi ya sureklilik arz edecek sekilde yada kademelI olarak makine parcasinin bir bolgesinden diger bir bolgesine dogru degismesi soz konusudur. Bu calisinada kullanilan fonksiyonel degisken inalzeme ler, birbiri icinde dairesel kademeli bir forma sahip olup SiC(p/AI-2124 kompozit sistemi esasina gore 400°C 'de sicak ekstruzyon ile uretilmislerdir. Uretilen fonksiyonel degisken malzemelerindis yuzeyi, Al-2124 matrix icine SiC parcaciklarinin takviye edilmesinden dolayi oldukca sert, kismi ise takviyesiz Al-2 124 alasimindan dolayi oldukca tok bir ozellik gosterir. Bu calismada bu malzemelerin cekme mukavemeti ozellikleri incelenm istir. Elde edilendeneysel so nuclar, teorik olarak gelistirilen fonnu 1lere gore hesaplanarak elde edilen sonuclar ile karsilasti rilmistir. Sonuc olarak, geleneksel kompozit malzemeler ile karsilastirildiginda, fonksiyonel degisken malzemelerin sunekliginin artmis oldugu fakat hafifce % 0.2 akma ve cekme mukavemetlerinde azalmanin mevcut oldugu tespit edilmistir.

Metallurgical and Materials Transactions A, 2001

Powder metallurgy processing involving cold pressing and hot extrusion has been used to fabricate... more Powder metallurgy processing involving cold pressing and hot extrusion has been used to fabricate bulk functionally graded materials (FGMs) based on the 2124/SiC/10p composite system. Two forms of single-core bulk FGMs with circular cross section were fabricated. One form (designated 10SiC-2124) had a central core of unreinforced Al-2124 alloy that was surrounded by a 2124/SiC/10p reinforced surface layer: the other (designated 2124-10SiC) had a composite core and an alloy surface layer. These forms enabled the effect of the radial graded core on fatigue to be investigated with fatigue crack propagation from either (1) a ductile core to a more brittle region or (2) a brittle core to a ductile region of the FGM. The fatigue crack growth rate was measured using a constant applied stress intensity factor range (⌬K ϭ 7 MPaΊm) technique. Two main fatigue crack growth rates were distinguished corresponding to growth in the core and in the surface layer. The results show that FGMs may exhibit good fatigue crack propagation resistance. For example, when the crack propagated from the brittle core to the tough surface layer, the average fatigue crack growth rate in the Al-2124 core (3.9 ϫ 10 Ϫ6 mm/cycle) was significantly lower than for the Al-2124 alloy (1.5 ϫ 10 Ϫ5 mm/ cycle) at a similar ⌬K value (7 MPaΊm), due to the highly tortuous crack path in the 2124/SiC/10p brittle layer. The 2124/SiC/10p brittle layer had a lower fatigue crack growth rate (6.6 ϫ 10 Ϫ6 mm/cycle) than the 2124/SiC/10p conventional composite (7.5 ϫ 10 Ϫ6 mm/cycle) because of the compressive residual stresses in the surface layer. Thus, FGMs could be more acceptable for critical applications than their conventional composite counterparts.

International Journal of Materials Research, Jun 1, 2010

The present study is focused on the effect of tool rotation speed on the microstructure and mecha... more The present study is focused on the effect of tool rotation speed on the microstructure and mechanical properties of butt welded dissimilar pure copper/brass alloy plates by friction stir welding. The joint performances were evaluated by microhardness measurements, tensile and bend tests. The results show that the grain size and the onion ring formation in the weld nugget zone and the mechanical properties of the joints were affected by tool rotation speed. It was found that the tensile strength of the joints was lower than that of the copper and brass base metals, while the bend strength was higher than that of the copper base metal and lower than the brass base metal. The highest mechanical properties were obtained from a tool rotation speed of 800 rpm at a travel speed of 22 mm min−1. The average microhardness values in the weld nugget zone increased with decreasing the tool rotation speed.

Periodicals of Engineering and Natural Sciences (PEN), Oct 3, 2013

The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase... more The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase steel by heattreatment at the chosen 730°C and 800°C intercritical temperature for 60 min followed by cold water quenching. The second aim of this study is to investigate the mechanical properties and the corrosion behaviours in 3.5% NaCl solution of Grade-A and dual-phase steels welded by flux-cored arc welding (FCAW). It was carried out the mass loss measurements and investigated the micro and macrostructures of welding zone using by optical microscope. The present study has demonstrated that Grade-A ship steel consisting of ferrite and pearlite can be successfully transformed to the dual-phase steel at the chosen intercritical temperatures. The microstructure of transformed dualphase steel consists of island of martensite in a ferrite matrix. The Grade-A and transformed dual-phase steels were successfully joined by FCAW. The mechanical results showed that the tensile strength of the transformed dual-phase steel were higher, but lower elongation than that of the Grade-A steel. The results from the immersion test in 3.5% NaCl solution showed that the corrosion behaviours of the dual-phase and Grade-A steels depend upon the morphology of the phase constituents. The corrosion rate of the transformed dual-phase steel with ferrite-martensite structure was lower than that of the Grade-A steel with ferrit-pearlite structure. The corrosion has preferential started at fusion line and progressed towards the heat affected zone (HAZ) of the welded dual-phase and Grade-A steels.

Journal of Iron and Steel Research, International, 2011

Grade A (GA) and high strength steel DH36 ship steels possessing different chemical compositions ... more 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

International Journal of Materials Engineering, 2019

In the present study, AA2124/25%vol.SiCp-T4 aluminum metal matrix composite plates were successfu... more In the present study, AA2124/25%vol.SiCp-T4 aluminum metal matrix composite plates were successfully friction stir butt joined using various welding parameters. The influence of the welding parameters on the distribution, micro-hardness and tensile strength of the joints was investigated and the joint efficiency was determined. The temperature measurements were obtained from four points at the each side of the weld, namely tool advancing and tool retreating side, from the 15 mm away from the weld center. Based on these measurements, the average peak temperature in the weld nugget was predicted according to studies in literature. As a result of the study, the temperature dissipation show that the max. 180-270 °C occurred at 15 mm away from the centerline of the weld. The maximum and minimum values of joint performance was obtained at 1400/40 and 1400/100 welding parameters as 73% and 59.32%, respectively. It was not detected a noticeable differences in micro-hardness measurements of ...

Journal of Composite Materials, 2011

The purpose of the study is to present the feasibility of the joining of similar AA2124/SiC/25p–T... more The purpose of the study is to present the feasibility of the joining of similar AA2124/SiC/25p–T4 composite plates by friction stir welding (FSW). Microstructure properties, microhardness, and tensile tests have been performed to evaluate the weld zone characteristics and the performance of AA2124/SiC/25p–T4 composite joints. The phase structure of a similar AA2124/SiC/25p–T4 composite weld was determined from X-ray diffraction (XRD). The temperature in the weld zone have been evaluated using thermocouples in order to demonstrate the FSWed joint of the AA2124/SiC/25p–T4 composite without melting. The obtained results revealed that FSW can be used in the joining of similar AA2124/SiC/25p–T4 composite plates. XRD measurements show that SiO2 phase was detected in the weld zones. It was determined that the peak temperatures achieved at 15 mm away from the weld center varied between 201°C and 270°C. In addition, the tensile strength of AA2124/SiC/25p–T4 butt joints was found to be appro...

In this study, the weldability of pure copper (Cu) plate to aluminum (Al-1050) plate has been inv... more In this study, the weldability of pure copper (Cu) plate to aluminum (Al-1050) plate has been investigated at a constant tool rotation speed of 515 rpm and different weld speeds by friction stir welding. While a relatively sound Cu/Al-1050 joint was achieved at the lowest weld speed (12 mm min), very poor joints were obtained at the higher weld speeds (30 and 50 mm min). Therefore in this study, microstructural characterization and mechanical properties of the joint at weld speed of 12 mm min were evaluated. Microstructure investigations by optical microscope and scanning electron microscope, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), tensile test and microhardness measurements were carried out in this joint. Microstructure inspections and EDS analysis revealed that the stir zone of the joint consisted of aluminum-rich and copper-rich structures. AlCu, Al2Cu3, AlCu4 and Al4Cu9 intermetallic compounds were detected in the weld region by XRD. Volume fraction ...

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Jun 1, 2000

Demir-Bakir ve Demir-Bakir-Grafit karisunlari olmak uzere iki farkli demir esasli malzeme toz met... more Demir-Bakir ve Demir-Bakir-Grafit karisunlari olmak uzere iki farkli demir esasli malzeme toz metalurjisi yonteini ile uretilmistir. Uretim islemi ise, tozlarin karistirilmasi, soguk presleme, 1125°C' de ve parcalanmis amonyak atmosferi altinda sinterleme vefirinda sogunna kademelerini icermektedir. Demir Bakir karisimlarinda bakir yuzdeleri %2 'den, %3.5' a kadar 0.5 adimlarla arttirilmistir. Demir-Bakir-Grafit karisimlarinda ise, bakir miktari sabit (%3) tutulurken,grafit miktari %0'dan %1.25'e 0.25 adimlarla arttirilmistir.

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Apr 1, 2002

Ozet -Petrol ve dogal gaz boru hatlarında yaygın olarak kullanılan ve tandem tozaltı kaynak metod... more Ozet -Petrol ve dogal gaz boru hatlarında yaygın olarak kullanılan ve tandem tozaltı kaynak metodu ile birleştirilen API 5L X65 d u al fazlı çeliğin kırılma to lduğu tespit edilmiştir. Kırılma to lduğu, çentikli üç nokta kırılma tokluğu deneyi kullanılara k belirlenmiştir. Çentik, hem kaynak dikişinin ortasına hem de ısının tesiri altındaki bölgesi (IT AB) içerisinin içine gelecek şekilde açılarak deney uygulanmıştır. Her bir nurnuneye gerilim giderme tavlaması uygulanarak, kırılma tokluğu değerlerinin nasıl etkilendiği değerlendirilmiştir. Elde edilen sonuçlara göre, gerilim giderme tavı uygulanmamış ve uygulanmış numunelerde, kaynak dikişinin kırılma to ld uğu, IT AB bölgesinin kırılma to lduğundan daha yüksek çıkmıştır. Anahtar Kelimeler -API 5L X65 çeliğinin kırılma tokluğu, spira l dikişli borular, tandem tozaltı kaynağı.

International Journal of Materials Research, Jul 1, 2012

ABSTRACT The aim of this study is to demonstrate the transformation of grade-A steel into dual-ph... more ABSTRACT The aim of this study is to demonstrate the transformation of grade-A steel into dual-phase steel by heat treatment, and the joint performance of dual-phase steels welded by means of the gas metal arc welding process using both solid and flux-cored welding wires. Dual-phase steels with different contents of martensite were obtained by intercritical annealing in different temperature ranges of a grade-A shipbuilding steel, followed by water quenching. The experimental results revealed that the tensile strength of the dual-phase steels joined by solid wire is higher than that of the flux-cored wire joints. The microstructure of grade-A steel consists of ferrite and pearlite, while the dual-phase steels consist of ferrite and martensite. On the other hand, while the martensitic phase is especially encountered in the weld metal of the dual-phase steels joined with the solid wire, the ferrite phase is more common in the weld metal of the flux-cored wire joints.

International Journal of Materials Research, Jun 1, 2010

Journal of Iron and Steel Research International, Aug 1, 2011

The mechanical and corrosion properties of gas metal arc additive manufacturing (GMA-AM) 316L cou... more The mechanical and corrosion properties of gas metal arc additive manufacturing (GMA-AM) 316L could be optimized by modifying the volume fractions of sigma(σ) and delta-ferrite(δ) phases through heat treatment. Results show that the heat treatment at 1000°C to 1200°C for one hour will not obvious influence the morphology of grains in steel but largely influence the contents of σ and δ phases. The heat treatment at 1000°C effectively increases the amount of σ phase in steel, causing both increase of UTS and YS but decrease of El and RA. The heat treatment at 1100°C to 1200°C completely eliminates σ phase, leading to the decrease of UTS and YS but increase of El and RA. The σ phase has better strengthening effect than δ phase, but which may degrade ductility and increase the possibility for cracks generation in steel. Meanwhile, limiting the number of both σ and δ phases through heat treatment can improve the corrosion resistance of steel. And σ phase appears more detrimental impact on degradation the corrosion resistance of steel than δ phase.

DergiPark (Istanbul University), Feb 20, 2013

Bu calismada, yuksek hiz celiginden imal edilen takim kullanilarak surtunme karistirma kaynak yon... more Bu calismada, yuksek hiz celiginden imal edilen takim kullanilarak surtunme karistirma kaynak yontemiylebirlestirilen AA2124/SiCp/25 kompozit levhalarin karisim bolgesi icerisinde takim asinmasindan dolayiolusabilecek metal veya fazlarin varligi incelenmistir. Takim asinma kaybi uzerine dusuk ve yuksek takimilerleme hizinin (40 mm/dak ve 100 mm/dak.) etkisi arastirilmistir. Karisim bolgesinin analizi, SEM, BEI veXRD calismalari ile yapilmistir. Yapilan deneysel calismalar sonucunda, sabit takim donme hizinda takimilerleme hizinin 40 mm/dak.’dan 100 mm/dak.’ya arttirilmasiyla, karistirici ucun uc kisminda %10, kokkisminda ise %5’ lik bir asinma kaybi belirlenmistir. Ayrica karisim bolgesi icerisinde karistirici uctan kopmusmetal parcaciklari, SiO2 ve Cu2FeAl7 metallerarasi fazlarin var oldugu XRD analizi ile tespit edilmistir. Buetkenlere bagli olarak, kaynak performansi % 42 oraninda dusus gostermistir.

DergiPark (Istanbul University), Sep 1, 2006

Özet-Günümüz endüstrisinde, metallerin kaynağı oldukça yaygın olarak kullanılmaktadır. Bu sahada ... more Özet-Günümüz endüstrisinde, metallerin kaynağı oldukça yaygın olarak kullanılmaktadır. Bu sahada çalışanların dikkate alması gereken en önemli konulardan biri iş güvenliği ve kaynakçının

DergiPark (Istanbul University), Feb 19, 2013

Bu çalışmada, saf bakır (Cu) ve alüminyum (Al-1050) levhaların, 515 min-1 sabit takım devir hızın... more Bu çalışmada, saf bakır (Cu) ve alüminyum (Al-1050) levhaların, 515 min-1 sabit takım devir hızında ve farklı kaynak hızlarında sürtünme karıştırma kaynağıyla alın-alına birleştirilebilirlikleri incelenmiştir. En düşük kaynak hızında (12 mm min-1) başarılı bir Cu/Al-1050 birleştirmesi elde edilebilirken, kaynak hızının 30 ve 50 mm min-1 e artmasıyla oldukça zayıf birleştirmeler gerçekleşmiştir. Bu nedenle çalışmada, 12 mm min-1 kaynak hızındaki birleştirmenin mikroyapı karakterizasyonu yapılmış ve mekanik özellikleri değerlendirilmiştir. Bu birleştirmede optik ve taramalı elektron mikroskobunda mikroyapı incelemeleri ile enerji dağılımlı X-ışınları spektroskopisi (EDS), X-ışınları difraksiyonu (XRD), çekme testi ve mikrosertlik ölçümleri gerçekleştirilmiştir. Mikroyapı incelemeleri ve EDS analizleri, karışım bölgesinin alüminyumca zengin ve bakırca zengin yapıları içerdiğini göstermiştir. Kaynak bölgesinin XRD incelemelerinde, AlCu, Al 2 Cu 3 , AlCu 4 ve Al 4 Cu 9 metaller arası bileşiklerin varlığı tespit edilmiştir. İmaj analiz programıyla bakırca zengin fazların karışım bölgesindeki hacimsel oranının yaklaşık %32 olduğu hesaplanmıştır. Çekme testi sonuçları, Cu/Al-1050 birleştirmesinin çekme mukavemetinin Cu ana metalinkinden %50, Al-1050 ana metalinkinden ise %24 düşük olduğunu göstermiştir. Mikrosertlik ölçümlerinde ise, karışım bölgesindeki sertliklerin ana metallere göre arttığı ve 74-280 HV arasında değiştiği görülmüştür.

Periodicals of Engineering and Natural Sciences (PEN), Oct 3, 2013

The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase... more The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase steel by heattreatment at the chosen 730°C and 800°C intercritical temperature for 60 min followed by cold water quenching. The second aim of this study is to investigate the mechanical properties and the corrosion behaviours in 3.5% NaCl solution of Grade-A and dual-phase steels welded by flux-cored arc welding (FCAW). It was carried out the mass loss measurements and investigated the micro and macrostructures of welding zone using by optical microscope. The present study has demonstrated that Grade-A ship steel consisting of ferrite and pearlite can be successfully transformed to the dual-phase steel at the chosen intercritical temperatures. The microstructure of transformed dualphase steel consists of island of martensite in a ferrite matrix. The Grade-A and transformed dual-phase steels were successfully joined by FCAW. The mechanical results showed that the tensile strength of the transformed dual-phase steel were higher, but lower elongation than that of the Grade-A steel. The results from the immersion test in 3.5% NaCl solution showed that the corrosion behaviours of the dual-phase and Grade-A steels depend upon the morphology of the phase constituents. The corrosion rate of the transformed dual-phase steel with ferrite-martensite structure was lower than that of the Grade-A steel with ferrit-pearlite structure. The corrosion has preferential started at fusion line and progressed towards the heat affected zone (HAZ) of the welded dual-phase and Grade-A steels.

Key Engineering Materials, May 1, 2004

The joining of functionally graded materials (FGMs) based on Al-2124/SiC(p) composite system to i... more The joining of functionally graded materials (FGMs) based on Al-2124/SiC(p) composite system to itself was carried out using a rotary friction welding technique. Mechanical powder metallurgy processing involving cold pressing and hot extrusion has been used to fabricate bulk functionally graded composites (FGCs) with single radial graded core. The central core of the single-core FGC was unreinforced Al-2124 alloy which was surrounded by a SiC reinforced surface layer. The influence of friction and forging pressures on the plastic deformation zone of single-core FGCs near the weld interface was investigated. The effect of unreinforced central core in the singlecore FGC on the plastic deformation and hardness of the welding zone were also reported. The results show that friction welding could be used to the joining of single-core functionally graded composites. Three different zones of the microstructure in the welding zone, namely Zud, Zpd and Zpl are observed. A SiC reinforced layer in the Zpl region was also observed. The width of welding zone is decreased with increasing the forging pressure.

At this work, it was aimed that to overcome the prejudice of society about Vocational and Technic... more At this work, it was aimed that to overcome the prejudice of society about Vocational and Technical Education (VET); to improve effective thinking methods and skills for VET by societies; to improve some suggestions to build cooperation between VET, labor market and employee for critical and analytical thinking way. The aim of this study is to determine the evaluation of what kind of methods needs to educate the students in Vocational and Technical Education (VET) according to what labor market needs; what kind of employee skills labor market requests; what VET schools make to educate the high skills employee; why the high practical skill employee requesting from labor market not to educate by VET; why the high practical skill employee frequently done the workplace switching; how young people encourage to go VET. For these purposes, it was organised Sakarya first vocational education workshop by the cooperation of Sakarya provincial directorate of National Education and East Marmara...

International Journal of Materials Research, 2010

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Jun 1, 2000

Fonksiyonel kademeli degisken malzemeler yeni bir kompozit malzeine turu dur. Bu malzemeler, bir ... more Fonksiyonel kademeli degisken malzemeler yeni bir kompozit malzeine turu dur. Bu malzemeler, bir makine parcasinin belirli bolgelerinde istenilen bir ozelligi elde etmek icin dizayn edilmis olup, malzeinenin kimyasal birlesimi, mikroyapisi ya sureklilik arz edecek sekilde yada kademelI olarak makine parcasinin bir bolgesinden diger bir bolgesine dogru degismesi soz konusudur. Bu calisinada kullanilan fonksiyonel degisken inalzeme ler, birbiri icinde dairesel kademeli bir forma sahip olup SiC(p/AI-2124 kompozit sistemi esasina gore 400°C 'de sicak ekstruzyon ile uretilmislerdir. Uretilen fonksiyonel degisken malzemelerindis yuzeyi, Al-2124 matrix icine SiC parcaciklarinin takviye edilmesinden dolayi oldukca sert, kismi ise takviyesiz Al-2 124 alasimindan dolayi oldukca tok bir ozellik gosterir. Bu calismada bu malzemelerin cekme mukavemeti ozellikleri incelenm istir. Elde edilendeneysel so nuclar, teorik olarak gelistirilen fonnu 1lere gore hesaplanarak elde edilen sonuclar ile karsilasti rilmistir. Sonuc olarak, geleneksel kompozit malzemeler ile karsilastirildiginda, fonksiyonel degisken malzemelerin sunekliginin artmis oldugu fakat hafifce % 0.2 akma ve cekme mukavemetlerinde azalmanin mevcut oldugu tespit edilmistir.

Metallurgical and Materials Transactions A, 2001

Powder metallurgy processing involving cold pressing and hot extrusion has been used to fabricate... more Powder metallurgy processing involving cold pressing and hot extrusion has been used to fabricate bulk functionally graded materials (FGMs) based on the 2124/SiC/10p composite system. Two forms of single-core bulk FGMs with circular cross section were fabricated. One form (designated 10SiC-2124) had a central core of unreinforced Al-2124 alloy that was surrounded by a 2124/SiC/10p reinforced surface layer: the other (designated 2124-10SiC) had a composite core and an alloy surface layer. These forms enabled the effect of the radial graded core on fatigue to be investigated with fatigue crack propagation from either (1) a ductile core to a more brittle region or (2) a brittle core to a ductile region of the FGM. The fatigue crack growth rate was measured using a constant applied stress intensity factor range (⌬K ϭ 7 MPaΊm) technique. Two main fatigue crack growth rates were distinguished corresponding to growth in the core and in the surface layer. The results show that FGMs may exhibit good fatigue crack propagation resistance. For example, when the crack propagated from the brittle core to the tough surface layer, the average fatigue crack growth rate in the Al-2124 core (3.9 ϫ 10 Ϫ6 mm/cycle) was significantly lower than for the Al-2124 alloy (1.5 ϫ 10 Ϫ5 mm/ cycle) at a similar ⌬K value (7 MPaΊm), due to the highly tortuous crack path in the 2124/SiC/10p brittle layer. The 2124/SiC/10p brittle layer had a lower fatigue crack growth rate (6.6 ϫ 10 Ϫ6 mm/cycle) than the 2124/SiC/10p conventional composite (7.5 ϫ 10 Ϫ6 mm/cycle) because of the compressive residual stresses in the surface layer. Thus, FGMs could be more acceptable for critical applications than their conventional composite counterparts.

International Journal of Materials Research, Jun 1, 2010

The present study is focused on the effect of tool rotation speed on the microstructure and mecha... more The present study is focused on the effect of tool rotation speed on the microstructure and mechanical properties of butt welded dissimilar pure copper/brass alloy plates by friction stir welding. The joint performances were evaluated by microhardness measurements, tensile and bend tests. The results show that the grain size and the onion ring formation in the weld nugget zone and the mechanical properties of the joints were affected by tool rotation speed. It was found that the tensile strength of the joints was lower than that of the copper and brass base metals, while the bend strength was higher than that of the copper base metal and lower than the brass base metal. The highest mechanical properties were obtained from a tool rotation speed of 800 rpm at a travel speed of 22 mm min−1. The average microhardness values in the weld nugget zone increased with decreasing the tool rotation speed.

Periodicals of Engineering and Natural Sciences (PEN), Oct 3, 2013

The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase... more The first aim of this study is to demonstrate the transformation of Grade-A steel into dual-phase steel by heattreatment at the chosen 730°C and 800°C intercritical temperature for 60 min followed by cold water quenching. The second aim of this study is to investigate the mechanical properties and the corrosion behaviours in 3.5% NaCl solution of Grade-A and dual-phase steels welded by flux-cored arc welding (FCAW). It was carried out the mass loss measurements and investigated the micro and macrostructures of welding zone using by optical microscope. The present study has demonstrated that Grade-A ship steel consisting of ferrite and pearlite can be successfully transformed to the dual-phase steel at the chosen intercritical temperatures. The microstructure of transformed dualphase steel consists of island of martensite in a ferrite matrix. The Grade-A and transformed dual-phase steels were successfully joined by FCAW. The mechanical results showed that the tensile strength of the transformed dual-phase steel were higher, but lower elongation than that of the Grade-A steel. The results from the immersion test in 3.5% NaCl solution showed that the corrosion behaviours of the dual-phase and Grade-A steels depend upon the morphology of the phase constituents. The corrosion rate of the transformed dual-phase steel with ferrite-martensite structure was lower than that of the Grade-A steel with ferrit-pearlite structure. The corrosion has preferential started at fusion line and progressed towards the heat affected zone (HAZ) of the welded dual-phase and Grade-A steels.

Journal of Iron and Steel Research, International, 2011

Grade A (GA) and high strength steel DH36 ship steels possessing different chemical compositions ... more 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

International Journal of Materials Engineering, 2019

In the present study, AA2124/25%vol.SiCp-T4 aluminum metal matrix composite plates were successfu... more In the present study, AA2124/25%vol.SiCp-T4 aluminum metal matrix composite plates were successfully friction stir butt joined using various welding parameters. The influence of the welding parameters on the distribution, micro-hardness and tensile strength of the joints was investigated and the joint efficiency was determined. The temperature measurements were obtained from four points at the each side of the weld, namely tool advancing and tool retreating side, from the 15 mm away from the weld center. Based on these measurements, the average peak temperature in the weld nugget was predicted according to studies in literature. As a result of the study, the temperature dissipation show that the max. 180-270 °C occurred at 15 mm away from the centerline of the weld. The maximum and minimum values of joint performance was obtained at 1400/40 and 1400/100 welding parameters as 73% and 59.32%, respectively. It was not detected a noticeable differences in micro-hardness measurements of ...

Journal of Composite Materials, 2011

The purpose of the study is to present the feasibility of the joining of similar AA2124/SiC/25p–T... more The purpose of the study is to present the feasibility of the joining of similar AA2124/SiC/25p–T4 composite plates by friction stir welding (FSW). Microstructure properties, microhardness, and tensile tests have been performed to evaluate the weld zone characteristics and the performance of AA2124/SiC/25p–T4 composite joints. The phase structure of a similar AA2124/SiC/25p–T4 composite weld was determined from X-ray diffraction (XRD). The temperature in the weld zone have been evaluated using thermocouples in order to demonstrate the FSWed joint of the AA2124/SiC/25p–T4 composite without melting. The obtained results revealed that FSW can be used in the joining of similar AA2124/SiC/25p–T4 composite plates. XRD measurements show that SiO2 phase was detected in the weld zones. It was determined that the peak temperatures achieved at 15 mm away from the weld center varied between 201°C and 270°C. In addition, the tensile strength of AA2124/SiC/25p–T4 butt joints was found to be appro...

In this study, the weldability of pure copper (Cu) plate to aluminum (Al-1050) plate has been inv... more In this study, the weldability of pure copper (Cu) plate to aluminum (Al-1050) plate has been investigated at a constant tool rotation speed of 515 rpm and different weld speeds by friction stir welding. While a relatively sound Cu/Al-1050 joint was achieved at the lowest weld speed (12 mm min), very poor joints were obtained at the higher weld speeds (30 and 50 mm min). Therefore in this study, microstructural characterization and mechanical properties of the joint at weld speed of 12 mm min were evaluated. Microstructure investigations by optical microscope and scanning electron microscope, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), tensile test and microhardness measurements were carried out in this joint. Microstructure inspections and EDS analysis revealed that the stir zone of the joint consisted of aluminum-rich and copper-rich structures. AlCu, Al2Cu3, AlCu4 and Al4Cu9 intermetallic compounds were detected in the weld region by XRD. Volume fraction ...