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Laser ışını, malzemenin yüzeyinden daha derin noktayaa, oluşan buhar kanalı aracılığı ile ulaşır. Malzeme içine çok yoğun bir enerji taşınımı gerçekleştirildiğinden, ısı yanımı için ısıl iletkenliğinin bu aşamadaki rolü ihmal edilecek kadar az olur. Ne var ki; türbülans olayları ile ergiyik banyonun geometrisinin oluşumu ve buna bağlı olarak da elde edilen kaynak dikişinin genişliğine, ısı iletiminin etkisi büyüktür. Kaynaklı birleşmeler, oluşturulmuş ergiyik fazın katılaşması ile elde edilir. Laser ile yüksek kaynak hızlarına ulaşıldığından, katılaşma hızı da görece yüksek olmaktadır, örneğin; çelik için 103-104 K/s katılaşma hızlarına ulaşılmaktadır. Bu nedenle özellikle alaşımsız ve düşük alaşımlı çeliklerin laser kaynağında mikroyapıya ve malzemenin son özelliklerine, soğumanın etkisi büyüktür. Bu çalışmada yapı çeliğinde laser ile kaynak edilebilirlik değerlerinin deneysel sonuçları verilmiş, yapı çeliği/ soğuk iş takım çeliği, sementasyon çeliği/küresel grafitli dökme demir, krom çeliği/sıcağa dayanıklı çelik, yapı çeliği/sert metal ve yapı çeliği/alüminyum çiftlerinin laser kaynak kabiliyetleri hakkında genel değerlendirmeler yapılmıştır.

International Iron & Steel Symposium
UDCS

Ahmet Karaaslan

Duplex stainless steels have equal amount of ferrite and austenite phases. Ferrite and austenite phase balance have been provided with solution treatment process. Solution treatment is applied between 1000 ˚C - 1200 ˚C and phase balance occurs due to applied solution treatment temperature and time. Microstructure properties such as ferrite and austenite phase proportions, ferrite grain size and grain boundary affect directly the corrosion behavior of the duplex stainless steels after the solution treatment. In this study, UNS32205 was solution treated between at 1100 ˚C and 1150 ˚C for 2 hours and 8 hours. Microstructure properties of the solution treated samples were characterized by light optical microscopy and image analysis. Moreover, electrochemical corrosion behavior of the samples was determined in 3.5% wt. NaCl solution.

International Iron & Steel Symposium
UDCS

Alptekin Kısasöz Ahmet Karaaslan

The effects of artificial aging on A356 aluminum billets were investigated. Low superheat casting (LSC) was performed in order to prepare appropriate samples by equiaxed grains formation instead of dendrites for further semi-solid metal process. Specimens were cast at 635°C in LSC technique and nondendritic grains were obtained. Produced billets were reheated at 595°C where both solid and liquid phases of the alloy coexist. Samples were held in this semi-solid region for varied times followed by quenching. After reheating step, specimens were solution treated, water-cooled and artificial aged. The microstructural evaluation and related hardness changing of reheated billets were examined by image analyser assisted light optical microscopy and Brinell hardness measurements. Aging process leads to attain relatively uniform microstructure with newly formed precipitates which provide increase in hardness considerably.

International Iron & Steel Symposium
UDCS

Ridvan Gecu Serhat Acar Alptekin Kısasöz Kerem Altug Guler Ahmet Karaaslan

Duplex stainless steels (DSSs) have both higher mechanical properties and corrosion resistance in the cause of austenitic and ferritic microstructure. DSSs, generally have equal amount of austenite and ferrite phases. Solution heat treatment is applied to DSSs for providing homogenous microstructure, composing desired austenite-ferrite phase fraction and resolving intermetallic phases. After the solution treatment, mechanical properties and corrosion resistance of DSSs can be alter, especially with changes in austenite-ferrite phase ratio. In this study, effect of solution treatment conditions on corrosion behaviour of EN 1.4462 was investigated. Solution treatments were applied at 1100˚C and 1150˚C for 2 hours and 8 hours. Corrosion test was applied in FeCl3 (10% wt.) media for solution treated specimens. Corrosion properties of the specimens were determined with weight loss and also, microstructural characterization was carried out by optical microscopy analysis.

International Iron & Steel Symposium
UDCS

Alptekin Kısasöz Ahmet Karaaslan

The AA7075 alloy has a wide range of applications due to its high strength and light weight. The T6 heat treatment applied to the AA7075 alloy increases the strength of the alloy but its corrosion properties remain poor. T73 heat treatment to increase the corrosion sensitivity reduces the strength of the alloy. A special heat treatment applied to the AA7075 alloy improves the corrosion and mechanical properties of the alloy at the same time.In this study, the effects of special heat treatment parameters applied to AA7075 alloy on alloy strength and corrosion were investigated.

International Iron & Steel Symposium
UDCS

Gökhan ÖZER Ahmet Karaaslan

In this study, AISI 2205 types of duplex stainless steels were welded by FCAW (flux cored arc welding) using E2209 T11/4 type flux cored filler metal. Joinings welded with different heat input and number of passes were characterized by microstructural analysis and charpy impact test. Also, ferrite/austenite phase ratios in welded specimens were investigated and variations in microstructural and mechanical properties were compared by ferrite/austenite phase balance. Moreover, effects of microstructural properties on mechanical properties of welded specimens were determined.

International Iron & Steel Symposium
UDCS

Alptekin Kısasöz Mustafa Tümer Ahmet Karaaslan

Abstract Metal matrix composites (MMCs) are obtained by the systematic combination of two or more different materials, at least one of which is metal, to provide desired and required properties. Metal matrix composite materials can provide properties that are not obtainable with conventional materials. Reinforcement materials in the form of particulates such as SiC are mainly used to fabricate MMCs. Important developments in tribological properties are achieved with the presence of hard particulates in the matrix structure [1-4].

International Symposium on Light Alloys and Composite Materials
UHAKS

Kubilay Öztürk Alptekin Kısasöz Ahmet Karaaslan