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Applicability of different powder and polymer recipes in a new design powder injection molding system
(Walter De Gruyter Gmbh, 2021) Cicek, Bunyamin; Sun, Yavuz; Turen, Yunus; Ahlatci, Hayrettin
Production methods are changing day by day with the developing technology. Based on this idea, a new production logic and machine have been developed owing to polymer-supported powder injection molding (PIM). The ability of this newly designed machine (newPIM) to mold metal or ceramic powders supported by polymer binders is discussed in this study. By taking advantage of the polymer properties such as fluidity and sticking, powders are molded with a specially developed machine with high gas pressure in certain sizes. In this study, in which many parameters are processed from feedstock (FS) production to molding; metals Mg/316L and ceramics SiC/SiO2 powders have been used in different powder sizes and structures. In the newPIM process, polymers were included in four different recipes. Paraffin wax (PW), polyethylene glycol (PEG), polypropylene (PP), ethylene-vinyl acetate (EVA), poly-methyl methacrylate (PMMA) and low-density polyethylene (LDPE) have been employed in the FS with different combinations. From FS production to the molding stage; pressure, microstructure examination, weight loss, and density change features were investigated. The result indicated that the best FS and molding was obtained by the PEG+PMMA polymer composition formed with a spherical powder with a diameter below 40 mu m. The compression force of the FS in this composition was observed at approximately 3.4k N values.
Bio-properties of Mg-RE alloys: an applied study on cytotoxicity and genotoxicity
(Taylor & Francis Ltd, 2024) Djebari, Kenza; Turen, Yunus; Elen, Levent; Ahlatci, Hayrettin; Bozer, Busra Moran; Cicek, Bunyamin
This study presents a comprehensive review of magnesium alloys with rare elements. It discusses Mg-RE alloys and includes an experimental process. Thus, the data obtained by examining Mg-RE alloys provided a better interpretation of the experimental study. In this study's investigation report, Mg-RE alloys were thoroughly analyzed. In the experimental part, the cytotoxic and genotoxic results of the rare elements added to the Mg-Zn-RE master alloy are discussed. Experiments were carried out by adding Nd and Ce to this master alloy in inverse proportions. In cytotoxic data, it was observed that the viability rate in bacteria increased by up to 200%. In addition, significant genotoxic results of Mg-RE alloys were obtained, which are uncommon in the literature. As a result, a new perspective on Mg-RE alloys has been created. Cette & eacute;tude pr & eacute;sente un examen complet des alliages de magn & eacute;sium contenant des & eacute;l & eacute;ments rares. Elle discute des alliages Mg-ER et comprend un proc & eacute;d & eacute; exp & eacute;rimental. Ainsi, les donn & eacute;es obtenues en examinant les alliages Mg-ER ont fourni une meilleure interpr & eacute;tation de l'& eacute;tude exp & eacute;rimentale. Dans le rapport d'investigation de cette & eacute;tude, on a analys & eacute; & agrave; fond les alliages Mg-ER. Dans la partie exp & eacute;rimentale, on discute des r & eacute;sultats cytotoxiques et g & eacute;notoxiques des & eacute;l & eacute;ments rares ajout & eacute;s & agrave; l'alliage m & egrave;re Mg-Zn-ER. On a r & eacute;alis & eacute; des exp & eacute;riences en ajoutant du Nd et du Ce & agrave; cet alliage m & egrave;re en proportions inverses. Dans les donn & eacute;es cytotoxiques, on a observ & eacute; que le taux de viabilit & eacute; des bact & eacute;ries a augment & eacute; jusqu'& agrave; 200%. De plus, on a obtenu des r & eacute;sultats g & eacute;notoxiques significatifs des alliages Mg-ER, qui sont peu communs dans la litt & eacute;rature. Par cons & eacute;quent, on a cr & eacute;& eacute; une nouvelle perspective sur les alliages Mg-ER.
Ca and Ce Effect on the Corrosion Resistance of Hot-Rolled AZ31 Mg Alloys
(Eos Assoc, 2020) Kara, Ismail Hakki; Yousef, Taher Ali Issa; Ahlatci, Hayrettin; Turen, Yunus
In this study, AZ31 Mg alloys with added Ca and Ce were produced by low pressure die casting and were rolled at 400 degrees C. The corrosion properties of the materials were determined by immersion test for 72 hours at a 3.5% NaCl solution. The microstructure of the samples was investigated by light optical microscopy (LOM) and scanning electron microscopy (SEM) before the corrosion test. Twins, dynamic recrystallization (DRX), and the alloying elements have an important role in imparting the final corrosion resistance of the investigated materials.
Characterization and corrosion behavior of composites reinforced with ZK60, AlN, and SiC particles
(Elsevier - Division Reed Elsevier India Pvt Ltd, 2023) Sager, Abdulmuaen; Esen, Ismail; Ahlatci, Hayrettin; Turen, Yunus
In this paper, microstructure, mechanical, immersion and potentiodynamic corrosion behaviours of extruded ZK60 matrix composites reinforced with forty-five lm 15% silicon carbide (SiC) particles and aluminium nitride nanoparticle (AIN) (0.2-0.5% 760 nm) were investigated. The SiC and AlN mixtures, which are the reinforcing elements of the composites, were first mixed with magnesium powder as the main alloy, then pressed under a pressure of 450 MPa and sintered at 420 degrees C. Second, the sintered compacts are placed in the ZK60 alloy matrix at the semi-solid melting temperature, and the melt is mixed mechanically. After the melts are mixed for 30 min and a homogeneous mixture is obtained, the mixtures are poured into metal moulds and composite samples are produced. After homogenization for 24 h at 400 degrees C, the composite samples were extruded at 300 degrees C with an extrusion ratio of 16:1 and a piston speed of 0.3 mm/s. Then, microstructure characterization of all composite samples was performed and potentiodynamic and immersion corrosion behaviours were analyzed in 3.5% NaCl solution. It was seen that the corrosion resistance increased depending on the percentages of SiC and AlN reinforcement elements in the matrix. As a result, it was seen that the potentiodynamic corrosion resistance of rein-forced ZK60 + 15% SiC (ZK60SiC15), ZK60 + 15% SiC + 02AIN (ZK60SiC15AlN0.2) and ZK60 + 15% SiC + 0.5% AIN (ZK60SiC15AlN0.5) compounds increased by 1.6, 1.8 and 3.5 times compared to the unre-inforced ZK60 alloy. The immersion corrosion rates were calculated as 2090.73, 1748.19, 1479.84 and 1397.79 (mg/year) for the unreinforced ZK60, ZK60SiC15, ZK60SiC15AlN0.2 and ZK60SiC15AlN0.5 rein-forcements, respectively. As a result of the SEM and elemental spectrum response analysis of the corro-sion surfaces, the presence of a layer rich in Si-O elements on the surface of the AlN + SiC reinforced composites enhanced corrosion resistance. Additionally, the formation of the Mg2Si intermetallics in the structure of the SiC reinforced composites improved corrosion resistance, according to the XRD results.(c) 2023 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
A COMPARATIVE STUDY ON THE MECHANICAL AND CORROSION PROPERTIES OF THE ZM20 AND ZM21 ALLOYS AFTER CASTING AND ROLLING
(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2022) Goren, Haul Ahmet; Unal, Mehmet; Turen, Junus; Ahlatci, Hayrettin; Sun, Yavuz
In this study, the effects of grain refinement and production methods on the corrosion, corrosive wear and mechanical properties of the as-cast and as-rolled Mg-2 wt.% Zn (ZM20) and Mg-2 wt.% Zn-0,51 wt.% Mn (ZM21) alloys were examined by using OM, XRD, SEM, hardness and uniaxial tensile test. Additionally, the potentiodynamic polarization, immersion corrosion test and corrosive wear properties of the ZM20 and ZM21 alloys were compared. According to the XRD results, MgZn and MgZn2 phases were found in the alloys and also MnZn3 phase occurred in the ZM21 alloy with the addition of manganese. Both during solidification forming nucleation points with the added manganese and during rolling the broken secondary phase particles distributed into the matrix prevented grain growth and led to the formation of a more refined structure. The tensile test results showed that the strength of the as-cast ZM21 alloys were better than that of the as-cast ZM20 alloys and further improvement in mechanical properties occurred with the rolling of the both alloys. The most superior hardness was found in the as-rolled ZM21 alloy. In the total 400-m recipro-cal corrosive wear test in the 3.5% NaCl solution, the lowest mass loss was in the as-rolled ZM21 alloys. In the potentiodynamic corrosion test, the highest corrosion resistance was occurred by the as-cast ZM20 alloy.
Comparison of calcium-magnesium-alumina-silicate (CMAS) resistance behavior of produced with electron beam physical vapor deposition (EB-PVD) method YSZ and Gd2Zr2O7/YSZ thermal barrier coatings systems
(Pergamon-Elsevier Science Ltd, 2021) Ozgurluk, Yasin; Karaoglanli, Abdullah Cahit; Ahlatci, Hayrettin
Thermal Barrier Coatings (TBCs) are generally used in both industrial gas turbines and aircraft engines. In this study, metal powders with CoNiCrAlY content were coated on Inconel 718 nickel-based superalloy substrate materials using the cold gas dynamic spray (CGDS) method, which is a new generation thermal spray coating method. As a top coating, YSZ and Gd2Zr2O7/YSZ (GZO/YSZ), respectively, single and double layer ceramic layers were deposited with an innovative method, physical vapor deposition by electron beam (EB-PVD). All produced TBC systems were sprinkled with vermiculite powder containing CMAS minerals and subjected to CMAS corrosion tests and the effect of CMAS damage on the phase stability and microstructure of TBC systems was determined using elemental mapping analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM). According to the results obtained, it has been determined that the double layer TBC system with GZO/YSZ is more resistant to CMAS damage than the single layer YSZ system.
Corrosion and Wear Behaviour of Boronized high Carbon and Chromium Cast Steel
(Iron Steel Inst Japan Keidanren Kaikan, 2013) Ahlatci, Hayrettin; Yargul, Gorkem; Cug, Harun; Cevik, Engin; Yasin, Suleyman; Sun, Yavuz
The purpose of this study was to examine the effect of boronising heat treatment on the corrosion behaviour (in two different corrosive media) and wear properties (on two different counter sliding discs) of the DIN 1.4777 quality cast steel containing 1.7% C, 30% Cr and 1.1% Si. The steel supplied as cast was exposed to homogenisation heat treatment at 1150 degrees C for 3,5 hours and then to boronising heat treatment at 900 degrees C for 8 hours using the powder of Ekabor 2. An optical light microscope, SEM and XRD analyses were used to conduct microstructural characterisation of the steel investigated. Electrochemical potentio-dynamic polarisation measurements were taken to evaluate corrosion behaviours of the examined steels. Wear tests were conducted in a pin-on-disc type wear device by using a load between 10 N and 60 N. While the corrosion resistance of the boronising heat treated steel deteriorated by the pitting damage mechanism within corrosive media, uniform corrosion damage enhanced the corrosion resistance of the examined boronised steel. Oxidative adhesion, cracking of oxide and/or boride layer, and severe plastic deformation mechanisms were dominant during the wear tests. Severe plastic deformation and cracking of the oxide and/or boride layer caused wear mechanism to transform from mild to severe.
Cyclic Hot Corrosion Failure Behaviors of EB-PVD TBC Systems in the Presence of Sulfate and Vanadate Molten Salts
(Mdpi, 2019) Ozgurluk, Yasin; Doleker, Kadir Mert; Ozkan, Dervis; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
The cold gas dynamic spray (CGDS) method has been considered a promising technology to produce a metallic bond coat for thermal barrier coating (TBC) systems. In this study, CoNiCrAlY bond coats produced by CGDS method were coated with yttria-stabilized zirconia (YSZ) by electron beam physical vapor deposition (EB-PVD). TBCs were subjected to 50 wt % V2O5 and 50 wt % Na2SO4 molten hot corrosion salt combinations at 1000 degrees C. In the case of YSZ top coat on TBCs, the reaction between Na2SO4, V2O5, and Y2O3 salts generates YVO4 crystals, and these structures cause the transformation of tetragonal ZrO2 to monoclinic ZrO2. This situation occurs under operating conditions that lead to TBC failure. Hot corrosion behavior and the related failure mechanisms of TBC systems were investigated and discussed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffractometer (XRD).
Dry Wear Behaviour of the New ZK60/AlN/SiC Particle Reinforced Composites
(Mdpi, 2022) Sager, Abdulmuaen; Esen, Ismail; Ahlatci, Hayrettin; Turen, Yunus
This study deals with the microstructure, mechanical, and wear properties of the extruded ZK60 matrix composites strengthened with 45 mu m, 15% silicon carbide particle (SiC) and 760 nm, 0.2-0.5% aluminium nitride (AlN) nanoparticle reinforcements. First, the reinforcement elements of the composites, SiC and AlN mixtures were prepared in master-magnesium powder, and compacts were formed under 450 MPa pressure and then sintered. Second, the compacted reinforcing elements were placed into the ZK60 alloy matrix at the semi-solid melt temperature, and the melt was mixed by mechanical mixing. After the melts were mixed for 30 min and a homogeneous mixture was formed, the mixtures were poured into metal moulds and composite samples were obtained. After being homogenized for 24 h at 400 degrees C, the alloys were extruded with a 16:1 deformation ratio at 310 degrees C and a ram speed of 0.3 mm/s to create final composite samples. After microstructure characterization and hardness analysis, the dry friction behavior of all composite samples was investigated. Depending on the percentage ratios of SIC and AlN reinforcement elements in the matrix, it was seen that the compressive strength and hardness of the composites increased, and the friction coefficient decreased. While the wear rate of the unreinforced ZK60 alloy was 3.89 x 10(-5) g/m, this value decreased by 26.2 percent to 2.87 x 10(-5) g/m in the 0.5% AlN + 15% SiC reinforced ZK 60 alloy.
Effect of 0.20% Beryllium (Be)-Added CuAl₁₀Ni₅Fe₄ Alloy on Tribological Behavior and Microstructural Properties After Post-Casting Heat Treatment and Forging Process
(MDPI AG, 2024-11-25) Khaled A. A. Babay; Esen, Ismail; Sagiroglu, Selami; Ahlatci, Hayrettin; Keskin, Esma
This study explored how post-casting heat treatment and forging affected the tribological and microstructural characteristics of 0.20% beryllium (Be)-added CuAl₁₀Ni₅Fe₄ alloys. The heat-treated CuAl₁₀Ni₅Fe₄ microstructure exhibits a copper-rich α (alpha)-solid-solution phase, a martensitic β (beta)-phase, and diverse intermetallic κ (kappa)-phases, such as leaf-shaped κI, thin κIII, and black globs. Adding 0.20% beryllium to CuAl₁₀Ni₅Fe₄ alloys enhanced the dendritic arm thickness, needle-like shape, and κ-phase quantities. Significant κIV- and κII-phase precipitation was observed in the tempered β-phase. Beryllium improves the aluminum matrix’s microstructure. Forging greatly reduced the microstructural thickness of CuAl₁₀Ni₅Fe₄ and CuAl₁₀Ni₅Fe₄-0.20% Be alloys. The forging process also developed new κIV-phases. Wear resistance and hardness improved with beryllium. The CuAl₁₀Ni₅Fe₄-0.20% Be alloy had the highest hardness values (235.29 and 255.08 HB) after solution treatment (ST) and tempering (T) after casting and forging (F). The CuAl10Ni5Fe4-0.20% alloy with Be added had the best wear after solution treatment, tempering, and forging. The CuAl₁₀Ni₅Fe₄-0.20% Be alloy demonstrated a 0.00272 g weight loss, a 1.36 × 10−8 g/N*m wear rate, and a 0.059 friction coefficient at 10,000 m after forging (F).
Effect of a 3.5% NaCl-10% HCl Corrosive Environment on the Fatigue Behavior of Hot Rolled Aluminum 5083-H111
(Mdpi, 2023) Elhasslouk, Masoud M. M.; Esen, Ismail; Ahlatci, Hayrettin; Akin, Bengu
This study deals with the microstructure of rolled Al5083-H111 materials, their hardness, corrosion in different solutions, and rotary bending fatigue properties of non-corroded and corroded samples in different solutions. This study is the first to report the fatigue behavior of corroded samples in different aggressive corrosion environments of Al5083. The microstructure of the Al5083-H111 material is in the form of grains oriented towards the rolling direction and it consists of binary Al-Mg, Al-Mn, and Mg-Si; ternary Al-Mg-Si; and quaternary Al-Mn-Fe-Si and Al-Cr-Mn precipitated randomly at the grain boundary. The Brinell hardness of the Al5083-H111 material is 68.67 HB. According to the results of the immersion corrosion, while the sample was more resistant to corrosion in a 3.5% NaCl environment, it showed a less resistant behavior in a 3.5% NaCl + 10% HCl environment. As a result of the fatigue test, it was observed that the sample that did not undergo corrosion showed a higher fatigue life than the samples that were exposed to corrosion. The fatigue rate of the 3.5% NaCl corrosion sample was 3.5 times lower than the fatigue rate of the 3.5% NaCl + 10% HCl corrosion sample.
Effect of Aging Heat Treatment on Wear Behavior and Microstructure Characterization of Newly Developed Al7075+Ti Alloys
(Mdpi, 2023) Nama, Hamza A. H. Abo; Esen, Ismail; Ahlatci, Hayrettin; Karakurt, Volkan
In this study, Al7075+0%Ti-, Al7075+2%Ti-, Al7075+4%Ti-, and Al7075+8%Ti-reinforced alloys were prepared by melting processes using Al7075 and Al-10%Ti main alloys. All newly produced alloys were subjected to T6 aging heat treatment and some samples were cold rolled at 5% beforehand. The microstructure, mechanical behavior, and dry-wear behavior of the new alloys were examined. Dry-wear tests of all alloys were carried out at a total sliding distance of 1000 m, at a sliding speed of 0.1 m/s, and under a load of 20 N. In the hardness measured after T6 aging heat treatment, the peak hardness of the Al7075+0%Ti-, Al7075+2%Ti-, Al7075+4%Ti-, and Al7075+8%Ti-reinforced alloys was found to be 105.63, 113.60, 122.44, and 140.41 HB, respectively. The secondary phases formed by the addition of Ti to the Al7075 alloy acted as precipitate-nucleation sites during aging heat treatment, further increasing the peak hardness. Compared to the peak hardness of the unrolled Al7075+0%Ti alloy, the increase in the peak hardness of the unrolled and rolled Al7075+8%Ti-reinforced alloys was 34% and 47%, respectively, and this difference in the increase was due to the change in the dislocation density with cold deformation. According to the dry-wear test results, the wear resistance of the Al7075 alloy increased by 108.5% with a reinforcement of 8% Ti. This result can be attributed to the formation of Al, Mg, and Ti-based oxide films during wear, as well as the precipitation hardening, the secondary hardening with acicular and spherical Al3Ti phases, the grain refinement, and solid-solution-hardening mechanisms.
Effect of carbon content and drawing strain on the fatigue behavior of tire cord filaments
(Elsevier - Division Reed Elsevier India Pvt Ltd, 2018) Koymatcik, Huseyin; Ahlatci, Hayrettin; Sun, Yavuz; Turen, Yunus
In this work we aim to investigate fatigue strengths of the steel filaments in diameter of 0.25 mm with three different Carbon (0.70%C, 0.80%C and 0.90%C) and with four different drawing strains (3.25, 3.37, 3.71 and 3.76) by the pure bending test method. All fatigue tests have been carried out at room temperature and at a frequency of 10 Hz via a custom manufactured pure bending testing machine of which the fully reserved strain value, R = epsilon(min)/epsilon(max), is -1. The applied value of cyclic deformation, epsilon, has been chosen from the range 0.20%-1.07% as bending strain. The plots of S-N (Strain-Cycle) curves are based on high cycle fatigue (HCF) life is greater than or equal to 10(4) cycles. The fatigue deformation limit values have been determined as 0.55% units and 0.20% units for the steels of the 0.25NT-70C and 0.25UT-90C quality, respectively. The increase in hardness resulting from the microstructural thinning (due to drawing strain) increases the fatigue deformation limit of the steels containing 0.80%C. Despite the increase in the drawing strain, carbon content and hardness, the fatigue deformation limit decreased with increasing inclusion content. Fractured surfaces of the samples, which have been broken at both high fatigue life and fatigue deformation limit values, are inspected via SEM. The SEM inspection has demonstrated that the fatigue fracturing of the steel filaments are similar to that of baseball bat cracking. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.
Effect of drawing strain on fatigue behavior of steel tire cord filaments
(Carl Hanser Verlag, 2018) Koymatcik, Huseyin; Ahlatci, Hayrettin
The experimental and numerically predicted fatigue strength of steel tire cord filaments used as reinforcing elements in automobile tires has been determined in this study by means of the pure bending test . The filaments had diameters of 0.20 and 0.25 mm and were produced under three distinct conditions of cold drawing strain quantified as 3.37, 3.68, and 3.71 %. All the fatigue tests were conducted at room temperature and at a frequency of 10 Hz via a custom manufactured pure bending tester with a fully reversible alternating strain value, R = epsilon(min)/epsilon(max), is -1. As the drawing strain value increased, the fatigue deformation limit increased parallel to an improvement in the mechanical properties. One can expect that an increase in drawing strain through a decrease in filament diameter will provide an improvement in the light weight design of cars.
The effect of GNPs on wear and corrosion behaviors of pure magnesium
(Elsevier Science Sa, 2017) Turan, Muhammet Emre; Sun, Yavuz; Akgul, Yasin; Turen, Yunus; Ahlatci, Hayrettin
This study aims to investigate the role of graphene on wear and corrosion behaviors of pure magnesium. Magnesium/Graphene Nanoparticle (GNP) composites were fabricated via semi powder metallurgy method with a different content of graphene (0.1, 0.25 and 0.5 wt%). The effect of graphene in pure magnesium was examined by hardness, wear and corrosion tests. Microstructural and phase analysis were carried out by Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis. Experimental results revealed that, hardness values increased with the addition of graphene. There was a same trend in wear behaviors with increase of graphene rate. The best wear performance was belonging to the 0.50 wt% graphene/mg composite under load of 10N. So improvement of wear properties was achieved using graphene as reinforcement. According to the microstructural evolution, the uniform distribution was achieved for all samples but partially agglomeration could be seen in Mg-0.50 wt% graphene. Compared to the pure magnesium, corrosion performance was affected negatively in graphene reinforced composites. (C) 2017 Elsevier B.V. All rights reserved.
The effect of head hardening process on the residual stress of rails
(Sage Publications Ltd, 2018) Turan, Muhammet E.; Ozcelik, Sait; Husem, Fazil; Ahlatci, Hayrettin; Sun, Yavuz; Tozlu, Ibrahim
In this study, the head hardening process was employed, by using a mixture of air and water under laboratory conditions, to improve the residual stress behavior of R260 grade rails . For this purpose, three types of specimens were selected. One group of rails was heated up to the austenite stage and then cooled for 20 s; the next group was heated up to the austenite stage and then cooled for 40 s and the third group was not exposed to any heat treatment. The hardness results showed that the specimens cooled for 40 s had excessive hardness; the specimens cooled for 20 s exhibited similar properties as that of R350HT rail standards, which are especially preferred in the lower radius of curvature bends in railways, but not that of R260. According to the analysis of residual stress, all samples had compressive residual stress, but the specimens cooled for 20 s had the highest stress value.
EFFECT OF INDIUM ADDITION ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AS-CAST AND HOT-ROLLED AM60 MAGNESIUM ALLOY
(Tanger Ltd, 2017) Zengin, Huseyin; Turen, Yunus; Ahlatci, Hayrettin; Sun, Yavuz
In this study, effect of indium (In) addition on microstructure and mechanical properties of AM60 magnesium alloys was investigated. In additions were made by 0.2, 0.5 and 1 wt.%. Alloys were produced by conventional gravity casting in a steel mould. A homogenization treatment at 350 degrees C for 24 h was performed after casting processes. Homogenized samples were 1 pass hot-rolled by 40 % thickness reduction at 350 degrees C. The results showed that the average grain size of as-cast and hot-rolled AM60 alloys decreased with In addition. SEM analysis revealed that In addition led to formation of tiny Mg-In binary second phases at triple junctions. Tensile strength of as-cast AM60 alloy increased with increasing amount of In up to 0.5 wt.% above which it decreased. However, after hot-rolling process, AM60 alloy containing 0.2 wt.% In showed the best tensile properties. These improvements were attributed to the refinement of microstructure and dispersion strengthening by Mg In intermetallic phases.
Effect of Oxidation Process on Mechanical and Tribological Behaviour of Titanium Grade 5 Alloy
(Mdpi, 2024) Saier, Abdulsalam; Esen, Ismail; Ahlatci, Hayrettin; Keskin, Esma
In this study, microstructural characterization, mechanical (tensile and compressive) properties, and tribological (wear) properties of Titanium Grade 5 alloy after the oxidation process were examined. While it is observed that the grey contrast coloured alpha grains are coaxial in the microstructures, it is seen that there are black contrast coloured beta grains at the grain boundaries. However, in oxidised Titanium Grade 5, it is possible to observe that the alpha structure becomes larger, and the number and density of the structure increases. Small-sized structures can be seen inside the growing alpha particles and on the beta particles. These structures are predicted to be Al-Ti/Al-V secondary phases. The nonoxidised alloy matrix and the OL layer exhibited a macrolevel hardness of 335 +/- 3.21 HB and 353 +/- 1.62 HB, respectively. The heat treatment increased Vickers microhardness by 13% in polished and etched nonoxidised and oxidised alloys, from 309 +/- 2.08 HV1 to 352 +/- 1.43 HV1. The Vickers microhardness value of the oxidised sample was 528 +/- 1.74 HV1, as a 50% increase was noted. According to their tensile properties, oxidised alloys showed a better result compared to nonoxidised alloys. While the peak stress in the oxidised alloy was 1028.40 MPa, in the nonoxidised alloy, this value was 1027.20 MPa. It is seen that the peak stresses of both materials are close to each other, and the result of the oxidised alloy is slightly better. When we look at the breaking strain to characterise the deformation behaviour in the materials, it is 0.084 mm/mm in the oxidised alloy; In the nonoxidised alloy, it is 0.066 mm/mm. When we look at the stress at offset yield of the two alloys, it is 694.56 MPa in the oxidised alloy; it was found to be 674.092 MPa in the nonoxidised alloy. According to their compressive test properties, the maximum compressive strength is 2164.32 MPa in the oxidised alloy; in the nonoxidised alloy, it is 1531.52 MPa. While the yield strength is 972.50 MPa in oxidised Titanium Grade 5, it was found to be 934.16 MPa in nonoxidised Titanium Grade 5. When the compressive deformation oxidised alloy is 100.01%, in the nonoxidised alloy, it is 68.50%. According to their tribological properties, the oxidised alloy provided the least weight loss after 10,000 m and had the best wear resistance. This material's weight loss and wear coefficient at the end of 10,000 m are 0.127 +/- 0.0002 g and (63.45 +/- 0.15) x 10-8 g/Nm, respectively. The highest weight loss and worst wear resistance have been observed in the nonoxidised alloy. The weight loss and wear coefficients at the end of 10,000 m are 0.140 +/- 0.0003 g and (69.75 +/- 0.09) x 10-8 g/Nm, respectively. The oxidation process has been shown to improve the tribological properties of Titanium Grade 5 alloy.
Effect of Rare Earth Elements (Y, La) on Microstructural Characterization and Corrosion Behavior of Ternary Mg-Y-La Alloys
(Mdpi, 2023) Alwakwak, Mohamed Ali Ibrahim; Esen, Ismail; Ahlatci, Hayrettin; Keskin, Esma
In this study, the microstructural properties and corrosion behavior of RE elements (Y, La) added to magnesium in varying minors after casting and homogenization heat treatment were investigated. Three-phase structures, such as & alpha;-Mg, lamellae-like phases, and network-shaped eutectic compounds, were seen in the microstructure results. The dendrite-like phases were evenly distributed from the eutectic compounds to the interior of the & alpha;-Mg grains, while the eutectic compounds (& alpha;-Mg + Mg) RE (La/Y)) were distributed at the grain boundaries. According to the corrosion results, the typical hydroxide formation for lanthanum content caused the formation of crater structures in the material, and with the increase in lanthanum content, these crater structures increased both in depth and in density. In addition, the corrosion products formed by Y2O3 and Y(OH)(3) in the Mg-3.21Y-3.15 La alloy increased the thickness of the corrosion film and formed a barrier that protects the material against corrosion. The thinness of the protective barrier against corrosion in the Mg-4.71 Y-3.98 La alloy is due to the increased lanthanum and yttrium ratios. In addition, the corrosion resistance of both Mg-3.21Y-3.15 La and Mg-4.71 Y-3.98 La alloys decreases after homogenization. This negative effect on corrosion is due to the coaxial distribution of oxide/hydroxide layers formed by yttrium and lanthanum after homogenization.
Effect of the additions of dehydrated geopolymer powders on compressive strength and integrity of the final geopolymer
(Korean Assoc Crystal Growth, Inc, 2015) Yasin, Suleyman; Ahlatci, Hayrettin
In this study, it is aimed to improve geopolymer compressive strength and integrity without causing any impurity. Thus, the effect of the additions of dehydrated geopolymer powders (0-40 wt.%) on compressive strength and integrity of the geopolymers cured with two different compositions was investigated. The powders were obtained by grinding of monolithic pure geopolymer which was dimensionally stabilised by thermally dehydration at 400 degrees C. Results of this study showed that when the powders were added at 10 wt.%, compactness of the microstructure and compressive strength of the samples increased. Additions of dehydrated geopolymer powder enhanced the integrity of the samples without changing the amorphous structure and typical FTIR spectrum of the pure geopolymers. Unlike the pure sample; after being thermally treated at 400 degrees C, the crack free samples, which had compressive strengths up to 51.65 Mpa could be obtained with the additions of the powders.

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