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Öğe Effect of heat treatment on the microstructures and mechanical properties of Al-5.5Zn-2.5Mg alloy(Elsevier Science Sa, 2016) Acer, Emine; Cadirli, Emin; Erol, Harun; Kirindi, Talip; Gunduz, MehmetThe Al-5.5 Zn-2.5 Mg (wt%) ternary alloy was prepared using a vacuum melting furnace and a casting furnace. Microstructural and mechanical properties of the alloy were investigated as-cast and under heat-treated conditions. To investigate the effect of heat treatment, numerous designed Al-5.5 Zn-2.5 Mg samples were homogenized under different conditions and then aged under different regimes. The effects of heat treatment on the microstructures were examined by OM, SEM, and TEM, and mechanical properties of the Al-Zn-Mg alloy were studied. A good combination of high microhardness and reasonable tensile strength were obtained by successive and suitable heat treatments. After aging for 24 h at 150 degrees C, the peak microhardnes and tensile strength values were achieved as 157 MPa and 188.8 MPa, respectively. The microscopic fracture surfaces of the aged samples under different homogenization and aging conditions were observed using scanning electron microscopy. Fractographic analysis of the tensile fracture surfaces shows that the type of fracture changed significantly from ductile to more ductile depending on the aging regime. (C) 2016 Elsevier B.V. All rights reserved.Öğe Effect of heat treatments on the microhardness and tensile strength of Al-0.25 wt.% Zr alloy(Elsevier Science Sa, 2015) Cadirli, Emin; Tecer, Hicran; Sahin, Mevlut; Yilmaz, Elif; Kirindi, Talip; Gunduz, MehmetIn the present work, the effect of heat treatments on the microhardness and tensile properties of the Al-0.25 Zr (wt.%) alloy have been investigated. The Al-0.25 Zr (wt.%) alloy was melted in a vacuum furnace, and the molten alloy was poured into crucibles held in a hot filing furnace. Then, the samples were directionally solidified from bottom to top and aged isothermally and isochronally in a muffle furnace. Aging was performed in two ways: using a wide range of temperatures (350-600 degrees C) with a constant aging time (100 h) and a wide range of aging times (3-240 h) with a constant temperature (400 degrees C). The dependence of the microhardness (HV) and ultimate tensile strength (sigma(UTS)) on the aging temperatures and aging times was determined. According to the experimental results, the HV and sigma(UTS) values of the aged samples increase at a certain aging temperature and aging time values, reaching peak values at specific temperatures and aging times. The microhardness and ultimate tensile strength decreased with further increase of aging temperatures and aging times. The microscopic fracture surfaces of the aged samples under different aging conditions were observed using scanning electron microscopy. Fractographic analysis of the tensile fracture surfaces shows that the type of fracture changed significantly from ductile to brittle depending on the aging times. Transmission electron microscopy was also used to characterize the precipitation processes in an Al-0.25 Zr (wt.%) alloy aged at 400 degrees C for 120 h. (C) 2015 Elsevier B. V. All rights reserved.Öğe EFFECT OF MN AMOUNT ON PHASE TRANSFORMATIONS AND MAGNETIC PROPERTIES IN Fe-Mn-Mo-Si ALLOYS(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2021) Armagan, Osman; Kirindi, TalipIn this study, microstructural and crystallographic properties of phase transformations occurring with thermal effect in Fe-XMn-Mo-Si (X = 15.14wt.% ye 18.45wt.%) alloys have been investigated. The effects of (wt.%) Mn rates in the alloy on the characteristics of phase transformations were investigated by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). SEM and TEM investigations was observed that two different martensite (epsilon and alpha') structures were formed in austenite grain. In addition, in TEM observations, the interface regions were selected over the bright field image. Crystallographic orientation relationships were obtained by the analyses of electron diffraction patterns from the interface regions. gamma -> alpha' type transformation was observed for a' particle formation, and orientation relationship was found as ((1) over bar 11)(gamma)//(011)(alpha'), [101](gamma)// [(1) over bar1 (1) over bar](alpha'), and, gamma -> epsilon type transformation was observed for epsilon martensite plate formation, and the orientation relationship was found as ((1) over bar1 (1) over bar))(gamma),(000 (2) over bar)(epsilon), //[(1) over bar(1) over bar0](gamma)//[(2) over bar 110](epsilon). It was noticed that this orientation relationships were compatible with the literature (Kurdjumov-Sachs and Shoji-Nishiyama orientation relationship). Precipitation phase (carbide) formation was observed in microstructure analyses. The changes in the magnetic properties of the alloys having different rates of Mn as a consequence of thermal effect phase transformations was investigated by using Mossbauer Spectroscopy. The internal magnetic field, volume fractions (transformation rates), isomer shift values and magnetic characteristics of the main and product phases were revealed by Mossbauer Spectroscopy. In the Mossbauer Spectrum, it was noticed that epsilon-martensite and gamma-austenite structures showed paramagnetic single-peak, and alpha'-martensite showed ferromagnetic six-peaks.Öğe The effects of pre-strain, recovery temperature, and bending deformation on shape memory effect in an Fe-Mn-Si-Cr-Ni alloy(Elsevier Science Sa, 2009) Kirindi, Talip; Sarı, Uğur; Dikici, MineIn this study, effects of pre-strain, recovery temperature, and number of bending test cycles on the microstructure and shape memory behavior of Fe-12.5%Mn-5.5%Si-9%Cr-3.5%Ni alloy have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM). X-Ray diffract-ion method, and bending test. Experiments show that the shape memory effect of the alloy can be enhanced by convenient recovery temperature and pre-strain rate. The shape recovery ratio increases with increasing pre-strain and recovery temperature, while it decreases with an increase in the number of bending test cycles. The changes in the shape memory are attributed to the variation of amount of epsilon martensite and crystal defects. The amount of epsilon martensite increases with increasing the pre-stain ratio. Crystal defects decrease with an increase in the recovery temperature, while they increase with increasing the number of the bending test cycles. (C) 2008 Elsevier B.V. All rights reserved.Öğe Effects of thermal and deformation on martensitic transformation and magnetic properties in Fe-17%Mn-4.5%X (X = Co and Mo) alloys(Pergamon-Elsevier Science Ltd, 2017) Armagan, Osman; Sari, Ugur; Yucel, Cagri; Kirindi, TalipIn this study, the Co and Mo addition to Fe-Mn based alloys was investigated to observe its effect on martensitic phase transformation. Two types of martensite structure occurred from the surface observations made by SEM for Co-added and Mo-added alloys morphologically in austenite grain. With the help of TEM studies, it was understood that these martensite structures are epsilon (h.c.p.) and alpha' (b.c.c.). TEM investigations showed that the orientation relationship between gamma (f.c.c.) and epsilon phases corresponds to Shoji-Nishiyama type and between gamma and alpha' phases corresponds to Kurdjumov-Sachs (K-S) type. In the SEM observations, the amount of these two types of martensite structure has been varied depending on the amount of deformation and the heat treatment temperature. In addition, Co and Mo effects were revealed in microstructure analyzes. By comparing the values of the lattice parameters obtained from the TEM and X-Ray observations with the values of those in the literature, it is shown how Co and Mo affect the lattice parameters of structure. The lattice parameter in Co-added alloy is a(alpha') = 2.8695 A degrees while Mo-added alloy is calculated as a(alpha') = 2.8567 A degrees. The type of martensitic transformation and the change of magnetic properties of alloys related to transformation rate were demonstrated by the analysis of the Mossbauer Spectrometer data. In particular, the change in the amount of alpha' martensite changes the antiferromagnetism or ferromagnetism and the internal magnetic field values of the alloys.Öğe Focusing-free impedimetric differentiation of red blood cells and leukemia cells: A system optimization(ELSEVIER SCIENCE SA, 2020) Bilican, Ismail; Guler, Mustafa Tahsin; Serhatlioglu, Murat; Kirindi, Talip; Elbuken, CaglarA focusing-free microfluidic impedimetric cell detection system is developed. The effect of the channel dimensions, solution conductivity, excitation voltage, and particle size on impedimetric signal outputs were optimized to increase the sensitivity of the system. Conventional microfabrication techniques were adapted to obtain low height, resealable microchannels. The geometry optimization was performed by a combination of analytical, numerical and experimental approaches. The results demonstrate that reliable impedimetric particle differentiation can be achieved without any labeling or particle focusing. The system parameters were studied and rule-of-thumb design criteria were provided. Finally, using the developed system, red blood cells and leukemia cells were experimentally detected and differentiated. Thanks to its simplicity, the focusing-free cell differentiation system may find applications in several cellular diagnostic uses.Öğe Mossbauer and electron microscopy study of martensitic transformations in an Fe-Mn-Mo alloy(Springer, 2010) Kirindi, Talip; Sarı, Uğur; Kurt, MetinThe kinetic, morphological, crystallographic, and magnetic characteristics of thermally induced martensites in Fe-13.4wt% Mn-5.2wt% Mo alloy were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Mossbauer spectroscopy. The experimental results reveal that two types of thermal-induced martensites, epsilon (hcp) and alpha' (bcc) martensites, are formed in the as-quenched condition, and these transformations have athermal characters. Mo addition to the Fe-Mn alloy does not change the coexistence of epsilon and alpha' martensites with the Mn content between 10wt% and 15wt%. Besides, Mossbauer spectra reveal a paramagnetic character with a singlet for the gamma (fcc) austenite and epsilon martensite phases and a ferromagnetic character with a broad sextet for the alpha' martensite phase. The volume fraction of alpha' martensite forming in the quenched alloy is much more than that of the epsilon martensite.
