Researcher:
Canadinç, Demircan

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Demircan

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Canadinç

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Canadinç, Demircan

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    Evolution of transformation plasticity in austenite-to-bainite phase transformation: a multi parameter problem
    (Elsevier Science Sa, 2012) Lambers, Hans -Gerd; Maier, Hans Jürgen; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433
    The current paper presents a thorough experimental analysis of the austenite-to-bainite phase transformation, and provides insight into microstructural changes associated with the observed transformation plasticity (TP). Specifically, the evolution of TP was studied in the presence of several parameters, namely pre-deformation, temperature and superimposed constant stresses, and the observed phenomena were linked to microstructural changes under these circumstances based on experimental data. One major finding is that the evolution of TP strains is governed both by the superimposed external stresses and the temperature dependence of internal stresses introduced by pre-deformation.
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    Dimensional stability of 51CrV4 steel during bainitic phase transformation under tensile and compressive stresses
    (Elsevier, 2010) Lambers H.-G.; Maier H.J.; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433
    The effect of the prior austenitization treatment on the stress-strain response of a low alloy 51CrV4 steel in its supercooled austenitic state and its effect on the evolution of transformation plasticity strain during a subsequent isothermal bainitic transformation was investigated. One of the key findings is that the prior austenitization treatment strongly affects the evolution of transformation plasticity strains during the subsequent isothermal bainitic transformation under stress, such that higher transformation plasticity strains are present when the austenite grain size is increased. In addition, higher 0.2% offset yield strengths of the supercooled austenite are present following an incomplete austenitization treatment due to the existence of residual carbides. Overall, the current results clearly lay out the effect of the prior austenitization treatment on the stress-strain response of the supercooled austenite and the evolution of transformation plasticity during bainitic transformation.
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    On the cyclic stability and fatigue performance of ultrafine-grained interstitial-free steel under mean stress
    (Trans Tech Publications Ltd, 2008) Niendorf, Thomas; Maier, Hans J.; Karaman, Ibrahim; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433
    This paper reports on the fatigue performance of an ultrafine-grained (UFG) interstitial-free (IF) steel deformed at various mean stress levels. The UFG microstructure was achieved using equal channel angular extrusion processing at room temperature (RT) and along an "efficient" route, giving way to the formation of high angle grain boundaries (HAGBs) with a high volume fraction. The current study not only confirms the previous finding that a high volume fraction of HAGBs promotes cyclic stability, but also inquires into the role of mean stress level on the cyclic stability. It is shown that the UFG IF steel exhibits a stable cyclic deformation response in the lowcycle fatigue regime within the medium applied mean stress range of -75 to 75 MPa. The corresponding fatigue lives can still be predicted with the Smith-Watson-Topper approach within this range. Furthermore, the present study demonstrates that the evolution of mean strains with cyclic deformation can be linked to the evolution of mean stresses in strain-controlled loading.
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    Dislocation activities in aluminum alloyed Hadfield steels
    (N/A, 2008) Şehitoğlu, Hüseyin; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433
    The work presented herein investigates the unusual strain hardening prevalent in Hadfield steel, which has not yet been linked to a clear cause, yet. The methodology adopted in this study is suppressing one of the dominant deformation mechanisms interactively dictating the work hardening of Hadfield steel, namely twinning and slip, and concentrating on the other. To achieve this end, Hadfield steel was alloyed with aluminium to increase the stacking fault energy, and thereby suppress twinning and give way to slip only. As a result of the thorough mechanical and micro structural analyses, we have concluded that the slip-related dislocation activities and the high-density dislocation walls brought about by slip in Hadfield steel significantly contribute to the work hardening of this material. / Öz: Bu çalışma, uzun bir süredir araştırılmasına rağmen, Hadfield çeliğinin henüz sebebi kesin olarak ortaya konulamayan olağan dışı sertleşme kapasitesine ışık tutmak amacıyla probleme değişik bir açıdan yaklaşmaktadır. Şimdiye kadar bu sertleşmenin sebebi olarak öne sürülen ve sertleşmeye olan katkıları birbirinden ayırt edilmesi güç olan ikiz ve kayma mekanizmalarından birini bastırarak diğerini inceleme yoluna gidilmiştir. Hadfield çeliği alüminyum ile alaşımlanarak dizim hatası enerji eşiği yükseltilmiş ve kayma mekanizmasının baskın olması sağlanmıştır. Yürütülen kapsamlı deneysel ve nümerik analizler sonucu varılan sonuç, aykırı yerleşim aktivitelerinin ve bunun doğal bir sonucu olan yüksek yoğunluklu aykırı yerleşim duvarlarının, Hadfield çeliğinin sertleşmesinde büyük katkı sahibi olduğunu ortaya koymuştur.
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    Modeling the role of external stresses on the austenite-to-bainite phase transformation in 51CrV4 steel
    (Institute of Physics (IOP) Publishing, 2011) Lambers, H-G; Tschumak, S.; Maier, H. J.; N/A; Department of Mechanical Engineering; Uslu, Mehmet Can; Canadinç, Demircan; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 23433
    A new model is proposed to successfully predict the initiation and evolution of the austenite-to-bainite phase transformation, capturing specifically the time-dependent transformation kinetics. In particular, the isothermal bainitic transformation in 51CrV4 steel is experimentally observed for various constant stress conditions, and significant improvement is obtained in comparison with the existing models. Specifically, both the transformation kinetics and the resultant transformation strains can be simultaneously predicted using the same variant growth approach. Simulation results are in good agreement with the experiments, evidencing the success of the proposed model in describing the transformation phenomena in terms of kinetics and transformation plasticity. Furthermore, the proposed formulation provides a basis for incorporating variant-variant interactions and cementite formation in the residual austenite matrix.
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    Modeling the role of hydrogen interstitial concentration on internal stress fields in iron matrix
    (Springer, 2010) Department of Mechanical Engineering; Department of Mechanical Engineering; Uslu, Mehmet Can; Canadinç, Demircan; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 23433
    A numerical model was proposed to predict the hydrogen interstitial concentration in iron matrix both in the immediate surrounding of and far from an edge dislocation. The current formulation successfully incorporates the relaxation effect and, thus, correctly predicts the stress state around the dislocations.
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    Accelerated oxidation in ductile refractory high-entropy alloys
    (Elsevier, 2018) Sheikh, Saad; Bijaksana, Muhammad Kurnia; Shafeie, Samrand; Lozinko, Adrianna; Gan, Lu; Tsao, Te-Kang; Klement, Uta; Murakami, Hideyuki; Guo, Sheng; N/A; Department of Mechanical Engineering; Motallebzadeh, Amir; Canadinç, Demircan; Researcher; Faculty Member; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; College of Engineering; N/A; 23433
    Refractory high-entropy alloys (RHEAs) are promising candidates for new-generation high temperature materials, but they generally suffer from room temperature brittleness and unsatisfactory high-temperature oxidation resistance. There currently lack efforts to address to these two critical issues for RHEAs at the same time. In this work, the high temperature oxidation resistance of a previously identified ductile Hf0.5Nb0.5Ta0.5Ti1.5Zr RHEA is studied. An accelerated oxidation or more specifically, pesting, in the temperature range of 600-1000 degrees C is observed for the target RHEA, where the oxidation leads the material to catastrophically disintegrate into powders. The pesting mechanism is studied here, and is attributed to the failure in forming protective oxide scales accompanied by the accelerated internal oxidation. The simultaneous removal of zirconium and hafnium can eliminate the pesting phenomenon in the alloy. It is believed that pesting can also occur to other equiatomic and non-equiatomic quinary Hf-Nb-Ta-Ti-Zr or quaternary Hf-Nb-Ti-Zr and Hf-Ta-Ti-Zr RHEAs, where all currently available ductile RHEAs are identified. Therefore, the results from this work will provide crucial perspectives to the further development of RHEAs as novel high-temperature materials, with balanced room-temperature ductility and high-temperature oxidation resistance.
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    The role of grain size and distribution on the cyclic stability of titanium
    (Pergamon-Elsevier Science Ltd, 2009) Niendorf, T.; Maier, H. J.; Karaman, İbrahim; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433
    The role of grain refinement and microstructural inhomogeneities on the cyclic stability of ultrafine-grained (UFG), coarse-grained and bimodal titanium of commercial purity was investigated. The observed superior fatigue performance and the proven biocompatibility of UFG Ti promote its utility as a biomaterial.
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    Twinning activity in high-manganese austenitic steels under high velocity loading
    (Taylor & Francis Ltd, 2016) Gerstein, G.; Maier, H. J.; N/A; N/A; Department of Mechanical Engineering; Gümüş, Berkay; Bal, Burak; Canadinç, Demircan; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 23433
    Deformation temperature and manganese content dependencies of twinning activity in two types of high Mn austenitic steels were investigated upon high velocity tensile loading. It was observed that nanotwin formation within previously formed twins dominates at subzero temperatures and significantly contributes to work hardening.
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    In-situ characterization of transformation plasticity during an isothermal austenite-to-bainite phase transformation
    (Elsevier Science Inc, 2012) Holzweissig, M. J.; Maier, H. J.; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433
    This paper elucidates the stress-induced variant selection process during the isothermal austenite-to-bainite phase transformation in a tool steel. Specifically, a thorough set of experiments combining electron backscatter diffraction and in-situ digital image correlation (DIC) was carried out to establish the role of superimposed stress level on the evolution of transformation plasticity (TP) strains. The important finding is that TP increases concomitant with the superimposed stress level, and strain localization accompanies phase transformation at all stress levels considered. Furthermore, TP strain distribution within the whole material becomes more homogeneous with increasing stress, such that fewer bainitic variants are selected to grow under higher stresses, yielding a more homogeneous strain distribution. In particular, the bainitic variants oriented along [101] and [201] directions are favored to grow parallel to the loading axis and are associated with large TP strains. Overall, this very first in-situ DIC investigation of the austenite-to-bainite phase transformation in steels evidences the clear relationship between the superimposed stress level, variant selection, and evolution of TP strains.