Investigation of the Mechanical, Electronic and Phonon Properties of X2ScAl (X = Ir, Os, and Pt) Heusler Compounds

In the present study, the second-order elastic constants and the electronic band structures of the X2ScAl (x = Ir, Os, and Pt) compounds crystallized in the L21 phase were calculated separately by using the ab-initio density functional theory. According to the results for the second-order elastic constants, these compounds met the Born mechanical stability criteria. Also, according to the Pugh criteria, they were found to have a ductile structure and to show anisotropic behavior. The microhardneses of the compounds were between 2 and 14 GPa, and the highest hardness was found in the Ir2ScAl (14.290 GPa) compound. In addition, the energy band structures of these compounds were calculated, and the crystals were found to have a metallic bond structure. All the computed data were compared with previously calculated results obtained with different methods. According to the findings obtained in the present study, in terms of its mechanical and electronic behaviors, Ir2ScAl was found to have better physical properties than Os2ScAl and Pt2ScAl. The phonon dispersion curves and their corresponding total and projected densities of states were investigated for the first time by using a linear-response approach in the context of density functional perturbation theory. The frequencies of the optical phonon modes of all compounds at the Γ point were 4.767, 7.504 and 9.271 THz for Ir2ScAl, 2.761, 7.985 and 9.184 THz for Os2ScAl and 2.012, 5.6952 and 8.118 THz for Pt2ScAl. The heat capacity Cv at constant volume versus temperature was calculated using a quasi-harmonic approach and the results are discussed. © 2020, The Korean Physical Society

Investigation of mechanical and electrical properties of Cu-%25 Mn-%11 Al alloy on heat treatment

YÖK Tez ID: 184279ÖZETCu-%25Mn-%11Al ALAŞIMININ MEKAN KSEL VE ELEKTR KSELÖZELL KLER ÜZER NE ISIL ŞLEM ETK LER N N NCELENMESYILDIZ, Yasin GöktürkKırıkkale ÜniversitesiFen Bilimleri EnstitüsüFizik Anabilim Dalı, Yüksek Lisans TeziDanışman: Prof. Dr. Tahsin Nuri DURLUŞubat 2006, 46 sayfaBu çalışmada, Cu-%25Mn-%11Al alaşımında oluşan austenite fazıiçerisindeki çökelti fazları Taramalı Elektron Mikroskobu (SEM) ile, bu çökeltifazlarının kütle oranları Enerji Dağılımlı X-Işınları Spektroskobisi (EDS)sistemi ile belirlenmiştir. Ayrıca alaşımın mekanik dayanımının belirlenmesiiçin zor-zorlanma, elektriksel özelliklerinin incelenmesi için elektriksel ölçümteknikleri kullanılmıştır. Elektron mikroskop incelemeleri sonunda Cu-%25Mn-%11Al alaşımında austenite tane yapısı ve çökelme sertleşmesi görülmüştür.Gözlenen bu fazların alaşıma uygulanan ısıl işleme ve soğutma hızına bağlıolduğu görülmüştür.Çökelme fazı gözlenen numune ile austenite fazı gözlenen numunekarşılaştırıldığında mekaniksel ve fiziksel olarak farklılıklar görüldü.iBu farklılıklara bakıldığında; içinde çökelme fazı gözlenen numuneninakma dayanımının, saf austenite faz yapısına sahip numunenin akmadayanımından %23.5 kadar daha yüksek olduğu görülmüştür. Bu iseçökelme sertleşmesinin austenite tane yapısına göre, alaşıma %23.5oranında bir sertlik kazandırdığını göstermiştir. Bunun yanında elektrikseldirence bakıldığında; çökelme fazı, austenite faza göre alaşıma %30 kadarelektriksel direnç kazandırmıştır.Anahtar Kelimeler: Çökelme sertleşmesi, zor-zorlanma, akma dayanımı,elektriksel direnç, taramalı elektron mikroskobuiiABSTRACTINVESTIGATION OF MECHANICAL AND ELECTRICAL PROPERTIES OFCu-%25Mn-%11Al ALLOY ON HEAT TREATMENTYILDIZ, Yasin GöktürkKırıkkale UniversityGraduate School of Natural and Applied SciencesDepartment of Physics, M. Sc. ThesisSupervisor: Prof. Dr. Tahsin Nuri DURLUFebruary 2006, 46 PagesIn this work, precipitation phases in an austenite phase in Cu-%25Mn-%11Al alloy were investigated by means of Scanning Electron Microscope(SEM) and mass ratios of these precipitate phases were determined byEnergy Dispersion X- Ray Spectroscopy (EDS). In addition, in order todetermine the mechanical strength of the alloy and its electrical properties,stress-strain and electrical measurement techniques were performedrespectively. The results of SEM measurements revealed that there are theaustenite grain structure and the precipitation hardening in Cu-%25Mn-%11Al alloy. It was also observed that the properties of these phasesdepend on the heat treatment and the cooling rate.iiiA comparision of the sample with the precipitation phase and austenitephase showed that there are differences in their mechanical and physicalproperties.During consideration of obtained different results, it was observed thatthe yield strength of the sample which contains precipitation was %23.5higher than the yield strength of the sample that was in pure austenite phase.Therefore, precipitation hardening has %23.5 higher contribution to theoverall alloy hardening. Furthermore precipitation phase contribute theoverall electrical resistivity %30 higher than the austenite phase.Keywords: Precipitation hardening, stress-strain, yield strength, electricalresistivity, scanning electron microscopy.i

Cu-%25Mn-%11Al alaşımının mekaniksel ve elektiriksel özellikleri üzerine ısıl işlem etkilerinin incelenmesi

Tez (Yüksek Lisans) -- Kırıkkale Üniversitesi87003

Tek Tabakalı Nanografende Lokal Spin Etkili Manyetizma

In this paper, we investigated local spin orientation (up or down) effects on magnetizations of the monolayer nanographene by using effective field theory developed by Kaneyoshi. It is found that the monolayer nanographene and its components have very small magnetization (mC1mC2mC3mMLNG2.31x10-180) at T0.00 for the Jd10 (C1-spin up, C2-spin down and C3-spin up). On the other hand, for Jd20, Jd30, Jd40, and Jd50, the monolayer nanographene and its components (C1, C2 and C3 atoms) have very large local spin induced magnetization (mC1mC2mC3mMLNG1;12.31x10-18) than those of the Jd10. These results clearly indicate that the local spin orientation in the monolayer nanographene has very strong effect on its magnetism.Bu çalışmada, Kaneyoshi tarafından geliştirilen etkin alan teorisi kullanılarak, tek tabakalı nanografenin mıknatıslanmalarına lokal spin yönelimlerinin (yukarı ya da aşağı) etkileri incelendi. Tek tabakalı nanografenin ve bileşenlerinin Jd10 (C1-spin yukarı, C2-spin aşağı ve C3-spin yukarı) için T0.00'da çok küçük mıknatıslanmaya (mC1mC2mC3mMLNG2.31x10-180) sahip olduğu bulundu. Diğer taraftan, Jd20, Jd30, Jd40 ve Jd50 için, tek tabakalı nanografen ve bileşenleri (C1, C2 ve C3 atomları), Jd10’dakinden çok büyük lokal spin etkili mıknatıslanmaya (mC1mC2mC3mMLNG;12.31x10-18) sahiptirler. Bu sonuçlar açıkça, lokal spin yönelimlerinin, tek tabakalı nanografenin manyetizması üzerinde çok güçlü bir etkiye sahip olduğunu göstermektedir

Fe-%30Ni-%3Pd alaşımında austenite-martensite faz dönüşümleri üzerine çalışmalar

Tez (Doktora) -- Kırıkkale Üniversitesi78472

Studies on the austenite-martensite phase transformations in an Fe-30%Ni-3%Pd alloy

YÖK Tez ID: 258958Bu çalışmada, Fe-%30Ni-%3Pd alaşımında termal etkiyle elde edilen martensitik dönüşümlerin kinetik, morfolojik, kristalografik ve manyetik özellikleri ile Ms sıcaklığının üzerindeki bir sıcaklıkta ön-zorlanmanın austenite faza etkisi ve ön-zorlanmadan sonra Ms sıcaklığı altına soğutularak elde edilen martensitik dönüşümlerin kinetik, morfolojik ve manyetik özellikleri incelendi.Alaşımda meydana gelen fazlara ait ana düzlemler ve her iki fazın örgü parametreleri X-ışınları kırınımı (XRD) metodu kullanılarak hesaplandı. Bu sonuçlara göre austenite (f.c.c.) yapı içerisinde sadece martensite (b.c.c.) yapının oluştuğu belirlendi. Martensitik dönüşümün kinetikleri (martensite başlama sıcaklığı (Ms), austenite başlama sıcaklığı (As) ve austenite bitiş sıcaklığı (Af)) Diferansiyel Taramalı Kalorimetre (DSC) ile tespit edildi. Bu yöntem ile martensitik dönüşüm kinetiğinin atermal karakteristikte olduğu ve ön-zorlanmanın Ms sıcaklığını düşürdüğü belirlendi.Oda sıcaklığında %5 ve %10 oranlarında uygulanan ön-zorlanma austenite fazda kayma çizgileri oluşturdu. % 5 ön-zorlanmadan sonra soğutmayla elde edilen martensite plakalarda kırılma ve bükülme, %10 ön-zorlanmadan sonra soğutmayla elde edilen martensite plakalarda ise küçülme, Taramalı Elektron Mikroskobu (SEM) kullanılarak gözlemlendi. Bunun yanında, Geçirmeli Elektron Mikroskobu (TEM) kullanılarak martensite fazın ince yapısı ve dönüşümün kristalografik özellikleri belirlendi. Austenite fazda oluşan martensite fazın Kurdjumov-Sachs türü kristalografik dönme bağıntısına uyduğu bulundu.Fe-%30Ni-%3Pd alaşımında oluşan martensite faza ait hacim yüzdeleri, martensite fazın iç manyetik alan ve izomer kayma değerleri Mössbauer Spektrometresi yöntemi kullanılarak belirlendi. Dönüşümün kinetikleri ve martensite plakaların morfolojisi üzerinde etkili olan ön-zorlanma, martensite fazın hacim oranını artırdı. Ayrıca Mössbauer spektrumlarından austenite fazın paramanyetik, martensite fazın ise ferromanyetik (ya da antiferromanyetik) özellikte olduğu açığa çıkartıldı.In this study, both the kinetics, morphological, crystallographic and magnetic properties of thermal induced and prestrain of austenite martensitic transformations in an Fe-30%Ni-3%Pd alloy were investigated. Effect of prestrain to austenite phase above the Ms temperature and kinetics, morphological, and magnetic properties of martensitic transformations which was formed by below the Ms temperature after the prestrain were investigated.X-ray diffraction method was used to calculate the lattice parameters which belong to phases in the alloy. According to these results, only austenite (f.c.c.) and martensite (b.c.c.) structures were determined in this alloy. Kinetics of martensitic transformation (martensite start temperature (Ms), austenite start temperature (As) and austenite finish temperature (Af) ) were determined by Diferential Scanning Calorimetry (DSC). Kinetics of the transformation was found to be as athermal type and Ms temperature decreased with increasing prestrain.5% and 10% prestrain which was applied to austenite phase at room temperature formed slip lines. Martensite plates, which were broken and bent, formed by cooling the alloy after 5% prestrain and martensite plates which were decrescent formed by cooling after 10% prestrain, observed by Scanning Electron Microscopy (SEM). Furthermore, substructure of martensite phase and crystalographic properties of transformation were investigated by Transmission Electron Microscopy (TEM). It was also found that the martensite which was formed in the austenite matrix exhibited a Kurdjumov-Sachs type orientation relationship.The volume fraction of martensite and austenite phases, the hyperfine magnetic field of martensite phase and isomery shift values in Fe-30%Ni-3%Pd alloy have been determined by using Mössbauer Spectroscopy. The pre-strain which are influential on the transformation kinetics and the martensite plates morphology, increased the rate of martensite volume. Moreover, the Mössbauer spectra of alloy showed a paramagnetic character for the austenite phase and a ferromagnetic (or antiferromagnetic) character for the martensite phase

First-Principles Study on PdMnSn and PtMnSn Compounds in C1 b Structure

The phase stability, the electronic, mechanic and lattice dynamical properties of C1b-type PdMnSn and PtMnSn compounds were investigated using first principles density functional calculations within the generalized gradient approximation. The computed lattice constants of PdMnSn and PtMnSn compounds were in line with the experimental and theoretical data in the published literature. The elastic constants in the C1b structure for PdMnSn and PtMnSn compounds were carried out using the energy-strain method. The computed values of three independent elastic constants, both compounds are mechanically stable in the C1-type crystal structure and met the stability criteria. The electronic structure, total and partial density values of states, and total magnetic moment of these compounds were calculated and the evaluations were carried out by comparing with the existing results. Dynamic properties of PdMnSn and PtMnSn compounds were obtained using the density functional perturbation theory. Both of the compounds were dynamically stable due to the absence of the imaginary phonon frequencies. In addition, it was found that the compounds had a rapid rise in specific heat capacities from 0 to 300 K

The effect of primary surgery in patients with stage IV breast cancer with bone metastasis only (protocol bomet MF14-01); a multi-center, registry study

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