AYTEKİN HİTİT - Academia.edu (original) (raw)
Papers by AYTEKİN HİTİT
Journal of Non-Crystalline Solids
In this study, the development of a furnace with the capability of vacuum arc melting and casting... more In this study, the development of a furnace with the capability of vacuum arc melting and casting is described. Melting process of the alloys with high melting temperatures can be achieved by this machine that involves controlled atmosphere and medium vacuum levels via electric arc. It was also aimed to produce metallic glasses with amorphous structure that needs rapid cooling processes. The design scaled for laboratory utilizes several methods applied for the production of metallic glass materials, such as drop casting, tilt casting, suction casting and piston-anvil casting methods. As a result, Cobalt-based bulk glassy alloys and composite structures coated with metallic glass were successfully produced and investigated the microstructural, mechanical and thermal properties of the alloys. © Afyon Kocatepe Universitesi
Materials Science and Engineering: A, 2020
ABSTRACT The effects of annealing on microstructure and mechanical properties of Ni36.3Co25W23.7B... more ABSTRACT The effects of annealing on microstructure and mechanical properties of Ni36.3Co25W23.7B15 bulk metallic glass are investigated. Composite samples were produced by annealing amorphous samples of the alloy above the crystallization temperature. Microstructural examinations revealed that nickel solid solution and CoWB phase precipitate upon annealing. Fully crystallized composite samples contain about 60 vol.% nickel solid solution and 40 vol.% CoWB phase. Microhardness of the amorphous alloy is determined to be 1168 HV. Composites having microhardness values higher than 1400 HV are obtained. Improvement in microhardness is caused by the formation of CoWB phase, whose microhardness is determined to be between 4500 and 5000 HV. This is the first composite reinforced by CoWB phase. Indentation fracture toughness of the composite having peak hardness ranges between 2.44 and 4.67 M P a m . It is found that further annealing results in slightly lower microhardness but higher indentation fracture toughness, which is between 3.55 and 6.45 M P a m . The effects of microstructure on microhardness and indentation fracture toughness of the composites are discussed.
Journal of Alloys and Compounds, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Metals and Materials International, 2016
Effect of Cu and Si substitutions for Co and B on the glass forming ability (GFA) of Co(43-x)CuxF... more Effect of Cu and Si substitutions for Co and B on the glass forming ability (GFA) of Co(43-x)CuxFe20Ta5.5B(31.5-x)Siy (x=0-1.5 and y=5-10) were systematically investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, and differential scanning calorimetry. In order to evaluate the contribution of copper and silicon, appropriate amounts of copper and silicon were individually introduced to the base alloy composition. By using the effects of copper and silicon together, significant enhancement was obtained and the critical casting thickness (CCT) of the base alloy was increased three times from 2 mm to 6 mm. Moreover, mechanical properties of the alloys were examined by compression tests and Vickers hardness measurements. The compression test results revealed that the glassy alloys having enhanced GFA shows high strength of about 3500-4000 MPa. In addition, existence of (Co,Fe)2B and (Co,Fe)20.82Ta2.18B6 crystalline phases in glassy matrix influences the hardnesses of the alloys compared to monolitic glassy structure having hardness of about 1200 Hv.
Journal of achievements in materials and manufacturing engineering, 2014
Journal of Materials Science & Technology, Feb 1, 2015
Effects of annealing temperature and time on microstructure and microhardness of Co 41 Ni 2 Fe 20... more Effects of annealing temperature and time on microstructure and microhardness of Co 41 Ni 2 Fe 20 Ta 5.5 B 26.5 Si 5 amorphous alloy have been investigated. Microhardness of the as-cast alloy is found to be 1170 HV. The maximum microhardness,1798 HV, is achieved after annealing the amorphous alloy at 1250 K for 10 min. Examination of the microstructure reveals that (Co,Fe) 2 B, (Co,Fe) 21 Ta 2 B 6 and (Co,Fe) 16 Ta 6 Si 7 phases precipitate in the matrix after annealing. Intrinsic hardness and HallePetch coefficients of the precipitates indicate that high hardness values result from precipitation of (Co,Fe) 2 B and (Co,Fe) 21 Ta 2 B 6 phases. It is also observed that increasing the annealing time results in the decrease in microhardness values because of the increase in particle sizes of the precipitates.
Metals, Dec 29, 2016
In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk me... more In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk metallic glasses were investigated as a function of iron content. Cylindrical samples of alloys with diameters of up to 4 mm were synthesized by a suction casting method in an arc furnace. Structures and thermal properties of the as-cast samples were determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. It was found that the critical casting thickness of the alloys reduced as iron content was increased and cobalt content was decreased. It was determined that GFA parameters, reduced glass transition temperature (T g /T l) and δ (= T x /(T l − T g)), show a very good correlation with critical casting thickness values. It was also observed that changing iron content did not effect thermal properties of the alloys.
Metals, Jan 28, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Acta Metallurgica Sinica (english Letters), Mar 21, 2015
Effects of tungsten and boron contents on the thermal properties and microhardness of W-Fe-B meta... more Effects of tungsten and boron contents on the thermal properties and microhardness of W-Fe-B metallic glass system were studied. Thin foils, with thicknesses of 20 and 100 lm, of the alloys were produced by piston and anvil method in an arc furnace. The structures of the foils were investigated by X-ray diffraction. Thermal stabilities of the alloys were examined by using differential scanning calorimetry. 20-lm-thick foils of all the alloys were determined to be fully amorphous, but crystalline phases were detected in the 100-lm-thick foils. It was found that crystallization temperatures of the alloys are between 1060 and 1177 K. Tungsten and boron content increases improve the crystallization temperature and microhardness of the alloys significantly, but deteriorate the glass forming ability of the alloys. It was also observed that for constant Fe content, increasing tungsten content to the level higher than that of boron content does not result in any further improvement in crystallization temperature, but improves glass forming ability significantly. The alloy containing highest total amount of tungsten and boron, W 35 Fe 35 B 30 , has the highest crystallization temperature, 1177 K, and microhardness, 1634 HV.
Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5... more Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5) metallic glasses have been investigated. For each alloy, thin sheets of samples having thickness of 20 µm and 100 µm were synthesized by piston and anvil method in a vacuum arc furnace. Also, 400 µm thick samples of the alloys were synthesized by suction casting method. The samples were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). Crystallization temperature of the base alloy, Ni51W31.6B17.4, is found to be 996 K and 5 at.% copper substitution for nickel increases the crystallization temperature to 1063 K, which is the highest value reported for Ni-based metallic glasses up to the present. In addition, critical casting thickness of alloy Ni51W31.6B17.4 is 100 µm and copper substitution does not have any effect on critical casting thickness of the alloys. Also, microhardness of the alloys are found to be around 1200 Hv, which is one of the highest microhardness values reported for a Ni-based metallic glass until now.
Metalik camlar yuksek dayanim, sertlik ve korozyon direnci gibi ustun ozelliklere sahiptirler. Fa... more Metalik camlar yuksek dayanim, sertlik ve korozyon direnci gibi ustun ozelliklere sahiptirler. Fakat metalik camlarin uretiminin zor olmasi ve yuksek safliktaki bilesenlerin kullanimi nedeniyle maliyetleri yuksektir. Bu sinirlamaya alternatif olarak metalik cam alasimlari kompozit bir malzeme bunyesine yuzey kaplama elemani olarak dahil edilirse, maliyet problemlerine cozum saglayabilecektir. Amorf yapiya sahip bir kaplamanin uretimi dusunuldugunde, hem hizli sogutma kosullarini karsilayan hem de kaplama malzemesini altlik yuzeyine yayabilen bir kaplama sistemine ihtiyac duyulur. Bu calismada kucuk parcalarin kaplanmasinda kullanilabilen pnonatik destekli bir sikistirma aparati tasarlanmistir. Bu yolla, sivi haldeki bir alasimin carpma etkisi ile altlik yuzeyine sikistirilmasi ve hizli bir sekilde sogutulmasi eszamanli olarak saglanmistir. Bu kapsamda, 20-80 μm kalinliginda ve Co43Cu1Fe20Ta5,5B26,5Si5 kompozisyonuna sahip amorf kaplamalar farkli metal altlik yuzeylerinde uretilmisti...
Metals, 2016
In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk me... more In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk metallic glasses were investigated as a function of iron content. Cylindrical samples of alloys with diameters of up to 4 mm were synthesized by a suction casting method in an arc furnace. Structures and thermal properties of the as-cast samples were determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. It was found that the critical casting thickness of the alloys reduced as iron content was increased and cobalt content was decreased. It was determined that GFA parameters, reduced glass transition temperature (T g /T l) and δ (= T x /(T l − T g)), show a very good correlation with critical casting thickness values. It was also observed that changing iron content did not effect thermal properties of the alloys.
Journal of Non-Crystalline Solids
In this study, the development of a furnace with the capability of vacuum arc melting and casting... more In this study, the development of a furnace with the capability of vacuum arc melting and casting is described. Melting process of the alloys with high melting temperatures can be achieved by this machine that involves controlled atmosphere and medium vacuum levels via electric arc. It was also aimed to produce metallic glasses with amorphous structure that needs rapid cooling processes. The design scaled for laboratory utilizes several methods applied for the production of metallic glass materials, such as drop casting, tilt casting, suction casting and piston-anvil casting methods. As a result, Cobalt-based bulk glassy alloys and composite structures coated with metallic glass were successfully produced and investigated the microstructural, mechanical and thermal properties of the alloys. © Afyon Kocatepe Universitesi
Materials Science and Engineering: A, 2020
ABSTRACT The effects of annealing on microstructure and mechanical properties of Ni36.3Co25W23.7B... more ABSTRACT The effects of annealing on microstructure and mechanical properties of Ni36.3Co25W23.7B15 bulk metallic glass are investigated. Composite samples were produced by annealing amorphous samples of the alloy above the crystallization temperature. Microstructural examinations revealed that nickel solid solution and CoWB phase precipitate upon annealing. Fully crystallized composite samples contain about 60 vol.% nickel solid solution and 40 vol.% CoWB phase. Microhardness of the amorphous alloy is determined to be 1168 HV. Composites having microhardness values higher than 1400 HV are obtained. Improvement in microhardness is caused by the formation of CoWB phase, whose microhardness is determined to be between 4500 and 5000 HV. This is the first composite reinforced by CoWB phase. Indentation fracture toughness of the composite having peak hardness ranges between 2.44 and 4.67 M P a m . It is found that further annealing results in slightly lower microhardness but higher indentation fracture toughness, which is between 3.55 and 6.45 M P a m . The effects of microstructure on microhardness and indentation fracture toughness of the composites are discussed.
Journal of Alloys and Compounds, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Metals and Materials International, 2016
Effect of Cu and Si substitutions for Co and B on the glass forming ability (GFA) of Co(43-x)CuxF... more Effect of Cu and Si substitutions for Co and B on the glass forming ability (GFA) of Co(43-x)CuxFe20Ta5.5B(31.5-x)Siy (x=0-1.5 and y=5-10) were systematically investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, and differential scanning calorimetry. In order to evaluate the contribution of copper and silicon, appropriate amounts of copper and silicon were individually introduced to the base alloy composition. By using the effects of copper and silicon together, significant enhancement was obtained and the critical casting thickness (CCT) of the base alloy was increased three times from 2 mm to 6 mm. Moreover, mechanical properties of the alloys were examined by compression tests and Vickers hardness measurements. The compression test results revealed that the glassy alloys having enhanced GFA shows high strength of about 3500-4000 MPa. In addition, existence of (Co,Fe)2B and (Co,Fe)20.82Ta2.18B6 crystalline phases in glassy matrix influences the hardnesses of the alloys compared to monolitic glassy structure having hardness of about 1200 Hv.
Journal of achievements in materials and manufacturing engineering, 2014
Journal of Materials Science & Technology, Feb 1, 2015
Effects of annealing temperature and time on microstructure and microhardness of Co 41 Ni 2 Fe 20... more Effects of annealing temperature and time on microstructure and microhardness of Co 41 Ni 2 Fe 20 Ta 5.5 B 26.5 Si 5 amorphous alloy have been investigated. Microhardness of the as-cast alloy is found to be 1170 HV. The maximum microhardness,1798 HV, is achieved after annealing the amorphous alloy at 1250 K for 10 min. Examination of the microstructure reveals that (Co,Fe) 2 B, (Co,Fe) 21 Ta 2 B 6 and (Co,Fe) 16 Ta 6 Si 7 phases precipitate in the matrix after annealing. Intrinsic hardness and HallePetch coefficients of the precipitates indicate that high hardness values result from precipitation of (Co,Fe) 2 B and (Co,Fe) 21 Ta 2 B 6 phases. It is also observed that increasing the annealing time results in the decrease in microhardness values because of the increase in particle sizes of the precipitates.
Metals, Dec 29, 2016
In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk me... more In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk metallic glasses were investigated as a function of iron content. Cylindrical samples of alloys with diameters of up to 4 mm were synthesized by a suction casting method in an arc furnace. Structures and thermal properties of the as-cast samples were determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. It was found that the critical casting thickness of the alloys reduced as iron content was increased and cobalt content was decreased. It was determined that GFA parameters, reduced glass transition temperature (T g /T l) and δ (= T x /(T l − T g)), show a very good correlation with critical casting thickness values. It was also observed that changing iron content did not effect thermal properties of the alloys.
Metals, Jan 28, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Acta Metallurgica Sinica (english Letters), Mar 21, 2015
Effects of tungsten and boron contents on the thermal properties and microhardness of W-Fe-B meta... more Effects of tungsten and boron contents on the thermal properties and microhardness of W-Fe-B metallic glass system were studied. Thin foils, with thicknesses of 20 and 100 lm, of the alloys were produced by piston and anvil method in an arc furnace. The structures of the foils were investigated by X-ray diffraction. Thermal stabilities of the alloys were examined by using differential scanning calorimetry. 20-lm-thick foils of all the alloys were determined to be fully amorphous, but crystalline phases were detected in the 100-lm-thick foils. It was found that crystallization temperatures of the alloys are between 1060 and 1177 K. Tungsten and boron content increases improve the crystallization temperature and microhardness of the alloys significantly, but deteriorate the glass forming ability of the alloys. It was also observed that for constant Fe content, increasing tungsten content to the level higher than that of boron content does not result in any further improvement in crystallization temperature, but improves glass forming ability significantly. The alloy containing highest total amount of tungsten and boron, W 35 Fe 35 B 30 , has the highest crystallization temperature, 1177 K, and microhardness, 1634 HV.
Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5... more Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5) metallic glasses have been investigated. For each alloy, thin sheets of samples having thickness of 20 µm and 100 µm were synthesized by piston and anvil method in a vacuum arc furnace. Also, 400 µm thick samples of the alloys were synthesized by suction casting method. The samples were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). Crystallization temperature of the base alloy, Ni51W31.6B17.4, is found to be 996 K and 5 at.% copper substitution for nickel increases the crystallization temperature to 1063 K, which is the highest value reported for Ni-based metallic glasses up to the present. In addition, critical casting thickness of alloy Ni51W31.6B17.4 is 100 µm and copper substitution does not have any effect on critical casting thickness of the alloys. Also, microhardness of the alloys are found to be around 1200 Hv, which is one of the highest microhardness values reported for a Ni-based metallic glass until now.
Metalik camlar yuksek dayanim, sertlik ve korozyon direnci gibi ustun ozelliklere sahiptirler. Fa... more Metalik camlar yuksek dayanim, sertlik ve korozyon direnci gibi ustun ozelliklere sahiptirler. Fakat metalik camlarin uretiminin zor olmasi ve yuksek safliktaki bilesenlerin kullanimi nedeniyle maliyetleri yuksektir. Bu sinirlamaya alternatif olarak metalik cam alasimlari kompozit bir malzeme bunyesine yuzey kaplama elemani olarak dahil edilirse, maliyet problemlerine cozum saglayabilecektir. Amorf yapiya sahip bir kaplamanin uretimi dusunuldugunde, hem hizli sogutma kosullarini karsilayan hem de kaplama malzemesini altlik yuzeyine yayabilen bir kaplama sistemine ihtiyac duyulur. Bu calismada kucuk parcalarin kaplanmasinda kullanilabilen pnonatik destekli bir sikistirma aparati tasarlanmistir. Bu yolla, sivi haldeki bir alasimin carpma etkisi ile altlik yuzeyine sikistirilmasi ve hizli bir sekilde sogutulmasi eszamanli olarak saglanmistir. Bu kapsamda, 20-80 μm kalinliginda ve Co43Cu1Fe20Ta5,5B26,5Si5 kompozisyonuna sahip amorf kaplamalar farkli metal altlik yuzeylerinde uretilmisti...
Metals, 2016
In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk me... more In this study, change in glass forming ability (GFA) and thermal stability of Co-Fe-based bulk metallic glasses were investigated as a function of iron content. Cylindrical samples of alloys with diameters of up to 4 mm were synthesized by a suction casting method in an arc furnace. Structures and thermal properties of the as-cast samples were determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. It was found that the critical casting thickness of the alloys reduced as iron content was increased and cobalt content was decreased. It was determined that GFA parameters, reduced glass transition temperature (T g /T l) and δ (= T x /(T l − T g)), show a very good correlation with critical casting thickness values. It was also observed that changing iron content did not effect thermal properties of the alloys.