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Öğe Alloying effect on K X-ray intensity ratios, K X-ray production cross-sections and radiative Auger ratios in superalloys constitute from Al, Ni and Mo elements(Elsevier Science Bv, 2010) Küp Aylıkçı, Nuray; Tıraşoğlu, Engin; Karahan, İsmail Hakkı; Aylıkçı, Volkan; Eskil, Murat; Cengiz, ErhanIn this study, sigma(K alpha,beta) production cross-sections, K-beta/K-alpha, KLM/K-alpha and KMM/K-beta RAE intensity ratios of Ni and sigma(K alpha), sigma(K beta 1,2) production cross-sections, K-beta 1,K-3/K-alpha, K-beta 2,K-4/K-alpha, K-beta 2,K-4/K-beta 1,K-3, KLM/K-alpha and KMM/K-beta RAE intensity ratios of Mo have been measured in pure metals and in superalloy specimens. The samples were excited by 59.5 keV gamma-rays from a Am-241 annular radioactive source. K X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The effect of alloying on the fluorescence parameters of Ni and Mo, phase structure, and corrosion behavior were investigated. The X-ray fluorescence parameters of Ni and Mo in superalloys indicate significant differences with respect to the pure metals. These differences are attributed to the reorganization of valence shell electrons and/or charge transfer phenomena in superalloys. (C) 2010 Elsevier B.V. All rights reserved.Öğe B2-L10 thermoelastic transformation on Ni50Mn29Sb12.5Co8.5 shape memory Heusler alloy(Springer Science and Business Media Deutschland GmbH, 2022) Eskil, Murat; Aldaş, KemalIn this study, a series of practically unique and valuable properties that occur with the structural phase transformation on the Shape Memory Ni50Mn29Sb12,5Co8,5 Heusler alloy with comparing different homogenization times, were investigated. From the results of X-ray diffraction (XRD) measurements carried out in this study, B2 ? ? (L10) structural phase transformation was observed. It has been understood that the alloy exhibits a ferromagnetic transition via Vibrating Sample Magnetometer (VSM) as well as the thermoelastic martensitic transformation detected by Differential Scanning Calorimetry (DSC) investigations. At the same time, it has been determined that the paramagnetic ? phase has B2 type bcc lattice structure. It has been determined that ? (B2) ? ? (L10) diffusionless phase transformation, which is considered as a structural phase transition occurring in the material, includes a martensitic mechanism with narrow temperature hysteresis. It was determined that the average lattice parameter of the B2 lattice was 2.956 Å. It was understood that the thick 110B2 reflection was divided into 110B2 and 111L10 peaks according to the measurements made between 42° and 44° angles. The diffraction peaks obtained in the study prove the existence of parallel L10 lamellae of the martensite phase with habit plane boundaries close to {110}B2. All these findings were supported by scattering electron microscope (SEM) and metal microscopy studies.Öğe Change on tetragonality of L10 phase with homogenization time on Ni50Mn29Sb21 shape memory heusler alloy(Springer, 2022) Eskil, Murat; Aldaş, KemalIn this study, the effects of homogenization heat treatment on microstructural and magnetic properties of the Ni50Mn29Sb21 shape memory Heusler alloy was investigated. Ni–Mn–Sb alloy system may be an important candidate to contribute on magnetic shape memory literatüre for practical applications. Based on the results of X-ray diffraction investigations, the B2 ? ? (L10) structural phase change was detected. Vibrating sample magnetometer and differential scanning calorimetry experiments revealed that the alloy exhibits a ferromagnetic transition as well as a thermoelastic martensitic transformation. At the same time, the B2 type bcc lattice structure of the paramagnetic phase has been established. A narrow temperature hysteresis has been discovered in the structural ? (B2) ? ? (L10) diffusionless martensitic phase transformation. The average lattice parameter of the B2 phase was calculated to be 2.942 Å. According to measurements taken between 41 and 47 deg, the thick 110B2 reflection was separated into two peaks: 110B2 and 111L10. Diffraction peaks demonstrate the occurrence of L10 martensite phase close to 110B2 habit plane borders. All these findings were supported by scattering electron microscope and metal microscopy analyses.Öğe Effect of Cryogenic Heat Treatment on Phase Formation in Co38Ni37Al17Si6Sb2 Ferromagnetic Shape Memory Alloy(Springer, 2021) Eskil, Murat; Şahan, Zeynep AylinIn this study, effect of cryogenic heat treatment in polycrystalline Co38Ni37Al17Si6Sb2 ferromagnetic shape memory alloy (FSMA) on phase formation phenomenon was investigated. After the homogenization process, the synthesized Co38Ni37Al17Si6Sb2 alloy was cooled into liquid nitrogen and kept in liquid nitrogen for different time periods. X-ray difraction method was used to determine lattice parameters and crystallite sizes from the samples obtained. The crystallite size of the Co38Ni37Al17Si6Sb2 alloy was calculated using the Debye Scherrer equation. The results show that these alloys were composed of four phases; A1 structure of ? phase, ? austenite phase (B2 cubic), body-centered tetragonal L10 martensite and ?? (ordered fcc L12) phase. Thermal properties of Co38Ni37Al17Si6Sb2 specimens were analyzed by Differential Scanning Calorimetry (DSC). Martensitic transformation temperatures were increased due to the increasing aging time in Liquid Nityrogen. An endothermic peak at ~ 165°C and an exothermic peak at ~ 110°C were observed from DSC results. Scattering Electron Microscope (SEM) and optical microscope experiments were performed to investigate metallographic structures. The findings of the ?, ? and L10 phases were confirmed by SEM observations and EDS analysis. As a result of cryogenic heat treatment in the material phase formation phonomenon was discussed. Vickers and Rocwell Hardness methods were determined to find differences of hardness values due to the cryogenic heat treatment time on Co38Ni37Al17Si6Sb2 FSMA. The hardness value of the alloy has been found to rise with increasing cryogenic aging time.Öğe Effect of extrusion on Ni55.5Mn25Ga18.5Mo2 shape memory Heusler alloy(Elsevier Ltd, 2023) Dal, Serkan; Eskil, Murat; Demirel, BilalIn this study, the effects of the extrusion process on the phase structure and shape memory properties of NiMn type Heusler alloy were investigated. For this, Ni55.5Mn25Ga18.5Mo2 alloy obtained by melting method in vacuum induction furnace was extruded at 950 °C, 1000 °C and 1050 °C, respectively. XRD analyzes of the obtained specimens were performed to compare crystallographic differences. Afterwards, metallurgical microscope and SEM photographs were obtained to see the phase structures of the specimens. Phase transformation temperatures were also determined by DSC analysis. In addition, EDS and MAPPING observations of elemental analysis were made. Then, Vickers micro-hardness analyses were performed to examine the effects of extrusion process on microhardness. As a result, the shape memory properties were negatively affected by the increase in extrusion temperature. Generally, with the increase in this temperature, the amount of high temperature phases increased significantly, as micro-hardness values slightly increased. In addition to this, martensitic phase structures decreased with increasing extrusion temperature and martensite and austenite transition temperatures could not be observed in DSC curves.Öğe Homojenizasyon süresinin NiMn alaşımında şekil hafıza davranışı üzerine etkisi(Aksaray Üniversitesi Fen Bilimleri Enstitüsü, 2022) Eskil, Murat; Aldaş, KemalSon yıllarda literatürde son derece dikkat çeken Ni-Mn-Sb ve Ni-Mn-Sb-Co şekil hafızalı alaşımlarına ısıl işlemlerle şekil hatırlama özelliği kazandırılabilmektedirler. Bu çalışmada; polikristal Ni50Mn29Sb21-xCox'in (x = 0 veya 8.5) manyetik şekil hafızalı alaşımlarının üzerinde homojenizasyon işleminin etkilerinin belirlenmesi ve Co katkısının, mikroyapı, manyetik ve sertlik özellikleri üzerindeki etkisine odaklanılmıştır. Çalışma esnasında gerçekleştirilen mikroyapı araştırmaları, X-ışını kırınım deneyleri tarafından ortaya konulduğu gibi homojenizasyon işlemine tabi tutulmuş durumda olan Ni50Mn29Sb21 ve Co katkılı Ni50Mn29Sb12.5Co8.5 alaşımın yüksek sıcaklıkta farklı fazlara (? (A1), B2 veya L21) sahip malzemeler olduğunu göstermektedir. L10, ve farklı katmanlı martensitlerle ilgili elde edilen veriler farklı yaklaşımlarla tartışılmıştır. Gerçekleştirilmiş olan metalografik gözlemler, katkı elementleri bakımından farklı bölgeler arasında önemli bir ayrım olan dendritik fazlı yapıyı ortaya koymaktadır. DSC ve Termomanyetik ölçümler aracılığıyla, incelenen alaşımlarında geçiş sıcaklıkları ile ilgili bilgi edinilmiştir. Vickers mikrosertlik ölçümlerine dayanarak yapılan mekanik özelliklerin incelenmesi, Co katkısının malzeme sertliği üzerindeki yararlı etkisi olduğunu göstermektedir.Öğe Phase evolution in Fe-Mn-Si shape memory alloys due to forging speed(World Scientific Publ Co Pte Ltd, 2013) Eskil, Murat; Kanca, ErdoğanThe objective of this investigation is to compare the crystallographic characteristics of two different compositions of Fe-Mn-Si alloys forged with the newly designed and constructed High Energy Rate Forming (HERF) hammer with conventional hydraulic and mechanical presses. The degree of martensite formation may depend on metal forming conditions. For both of the alloys, one of the specimens was investigated in as "prepared form", the other specimen was investigated after air cooling with homogenization treatment and three specimens were deformed in different velocities after homogenization treatments. The changes which occurred in the transformation parameters of two FeMnSi alloys with different compositions due to the effects of thermal and mechanical procedures have been studied by using X-ray diffraction. In the alloy specimens cooled to different conditions from the high-temperature gamma phase region, gamma -> epsilon and gamma -> epsilon -> alpha' martensitic transformations were observed. The lattice parameters (LP) of fcc gamma and hcp epsilon structures were determined, and changes in forging speed on the LPs were found.Öğe Prediction of A(f) temperature for copper based shape memory alloys(National Institute of Science Communication and Information Resources (NISCAIR), 2014) Aldaş, Kemal; Özkul, İskender; Eskil, MuratThis study presents the gene expression programming (GEP) soft computing technique as a new tool for the formulation of the Austenite finish (Af) temperature of Cu-based shape memory alloys (SMA) for various compositions and heat treatments. The objective of this study is to provide an alternative formulation to related design composition and verify the robustness of GEP for the formulation of such structural problems. The training and testing patterns of the proposed GEP formulation is based on well established experimental results from the literature. The GEP based formulation results are compared with the experimental results and found to be quite reliable. © 2014, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Öğe Prediction of surface roughness in longitudinal turning process by a genetic learning algorithm(Carl Hanser Verlag, 2014) Aldaş, Kemal; Özkul, iskender; Eskil, MuratThe surface roughness is one of the major parameters for determining the level of machining quality. The cutting parameters and conditions have great importance to achieve the desired values during the turning process. In the present work, a new approach was considered for modelling the effect of various turning process parameters and conditions on surface roughness. The experimental studies about the surface roughness after the turning process documented in the literature were collected and compiled into a model based on a genetic learning algorithm. As input parameters for modeling the work piece alloy type, tool type, tool tip radius, tool coating type, cooling conditions, cutting speed, feed rate, and cut depth were used in the study and were comprehensivly compiled.Öğe Prediction of thermodynamic equilibrium temperature of Cu-based shape-memory smart materials(Springer, 2015) Eskil, Murat; Aldaş, Kemal; Özkul, İskenderThe thermodynamic equilibrium temperature (T (0)) is an important factor in the austenite and martensitic phases. In this study, the effects of alloying elements and heat treatments on T (0) temperature were investigated using Genetic Programming (GP) which has become one of the tools used in the study of condensed matter. Due to the changes in T (0), it is possible to analyze the changes in the entropy of the phase transitions. The data patterns of the GP formulation are based on well-established experimental results from the literature. The results of the GP-based formulation were compared with experimental results and found to be reliable with a very high correlation (R (2) = 0.965 for training and R (2) = 0.952 for testing).Öğe The effect of aging temperature on transformation parameters of porous NiTi shape memory alloy fabricated by SHS(Allerton Press Inc, 2013) Eskil, MuratThis study reports some different and efficient approaches for the aging temperatures which cause changes in the transformation parameters of porous NiTi (Ti-50.5 at % Ni) shape memory alloy (SMA) with porosity of 55.3% fabricated by self propagating high temperature synthesis (SHS). Changes which occurred in phase transformations due to the effects of various thermal procedures have been investigated by using X-ray diffraction. The micro structure was investigated using a scattering electron microscope and a light optical microscope. The shape memory behavior and transformation temperatures were studied through the differential scanning calorimetry (DSC). During the compression tests, it was observed that the compressive strength of the specimens was higher than the compact human bone, and that it increased with increasing aging temperature.Öğe The effects of homogenization time on the crystal structure and hardness of NiMnGaMo alloy(Elsevier, 2021) Dal, Serkan; Demirel, Bilal; Eskil, MuratThis study is based on X-ray diffraction (XRD) and DSC analysis, Scanning Electron Microscopy (SEM) and Optical Microscope observations and Vickers Micro Hardness Test results with structural effect and phase transformations on NiMnGa shape memory alloys with different composition. The addition of different elements to the shape-memory NiMnGa alloys and the heat treatment of the alloys are extremely useful for improving the shape memory, magnetic, mechanical, chemical and other physical properties. The NiMnGaMo alloys were successfully obtained using a vacuum induction melting furnace and then homogenized by heat treatment at 950 degrees C for 2, 24 and 96 h, respectively. After homogenization, all samples were cooled in ice water. Crystallographic results calculated from XRD data were evaluated by comparison with the data obtained by DSC analysis, Scanning Electron Microscope (SEM), Optical Microscope and Vickers Micro Hardness Test Device. The results show that the alloy with a higher Mo amount has a smaller crystallite size and the L2(1) lattice volume increases with heat treatment time. The change on microhardness values were discussed with the change on the obtained lattice constants.Öğe Thermodynamic and crystallographic properties of gamma radiated shape memory Cu-Al-Be alloy(Springer Science and Business Media Deutschland GmbH, 2021) Nevin Balo, Ş.; Eskil, MuratThe effect of the different doses of ? irradiation on Cu–23.36Al–2.78Be (at.%) shape memory alloy (SMA) has been investigated in this study. The effect of irradiated dose on characteristic transition temperatures was determined by differential scanning calorimetry (DSC). The diffraction planes which depend on irradiation dose were analyzed by X-ray diffraction (XRD), and crystallite size was calculated for alloy samples. In order to observe changes in the structure with increasing irradiation dose, optical microscope investigations were performed. The transformation temperatures and activation energies decreased after irradiation, and some changes occurred in the forming latent gas. The sample of the heat treated but unirradiated alloy includes the ? (DO3) structure as matrix phase at room temperature. With increasing irradiation dose, 18 R martensite structure is observed. Microhardness values and crystallite size values of the alloy samples changed significantly with increasing irradiation dose. The average crystallite size was found as 42.99 × 103 ± 18.71 nm for Cu–23.36Al–2.78Be (at.%) SMA. The thermal measurements showed a non-monotonous change on transition temperatures by the increase in applied dose value. Radiation hardening is about the beginning of spot defects in the metal structure. The basis of the mechanism is the interaction of the defects with movement of dislocations. Under the effect of radiation, very fast moving atomic particles strike the atoms that make up the crystal structure and force them out of their balanced position. As a result, atomic cavities and some defect atoms are formed in the lattice because of the gamma radiation.
