Derya Dispinar

Derya Dispinar
Istanbul Technical University · Department of Metallurgical and Materials Engineering

Assoc.Prof.Dr.

About

193
Publications
78,800
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1,566
Citations
Citations since 2017
88 Research Items
1140 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250

Publications

Publications (193)
Article
Mechanical properties of the castings are directly affected negatively by the inclusions, such as its own oxide occurring during melting, if proper and logical liquid metal processes could not be carried out. To overcome this issue, different compositions and types of fluxes were practiced. Na2SiF6, NaF/AlF3 (cryolite ratio) = 1.85, 2.8, and 3, NaF...
Article
Additive manufacturing has great advantages to produce complex shapes. • Recycling of AM aluminum was investigated for the first time. • Material loss due to high surface area was high in recycled AM around 17%. • Yield and ultimate tensile strength were in acceptable range. • Elongation at fracture was scattered with low reliability due to unmelte...
Article
In this study, the effects of the oxide films formed by using different mold cavity geometries on the mechanical properties of the parts were investigated. The casting process was carried out using the same runner system with different mold geometries. The effect of liquid metal flow rate on bifilm formation and the mechanical properties of the cas...
Article
Full-text available
The determination of types of defects that may be present in aluminum alloys has been a long-going discussion. Porosity has been held responsible for many of the failures in cast aluminum alloys. Due to the dramatic decrease in the solubility of hydrogen from liquid to solid aluminum, hydrogen is believed to be released from the solidification fron...
Article
Full-text available
Porosity is one of the challenges in high-pressure die casting (HPDC) of aluminum alloys. A typical control of porosity involved controlled solidification which is attained by the cooling of the die. In traditional cooling, this is done by straight cooling channels. However, they can be ineffective due to the limited geometry of these channels. Alt...
Article
Full-text available
This paper reports the synthesis and the performance of polymer-derived ceramic filters for molten metal filtration. Two different filter types were studied: foam filters produced from flexible polyurethane (PU) foams and additive manufacturing (AM) filters produced from thermoplastic polyurethane (TPU) cellular structure, and the results from all...
Article
Alüminyum alaşımlarının döküm yoluyla üretilmesindeki önemli kusurlardan birisi sıcak yırtılmadır. Bu çalışmada, farklı özelliklere sahip 1050 ve 5083 döküm alaşımlarının sıcak yırtılmaları araştırılmış ve sıcak yırtılmaya neden olan tasarım parametreleri ile döküm koşulları belirlenmiştir. Ayrıca sıcak yırtılmanın metalografik ve mekanik özellikle...
Chapter
Al-Si alloys are an attractive choice of light alloys due to their low density and high mechanical properties. The application areas include automotive and aerospace parts. With the increased requirements and demands on such applications, the researchers have focused on the enhancement of properties with the addition of novel alloying elements. In...
Article
Grain refinement of Al–Si alloys has been a long subject of study with various theories still being discussed. The efficiency of grain refiners, fading effect, poisoning effect, and selection of the optimum ratios of particularly Ti/B ratio has been the focus of many researchers. In this work, different grain refiners were added to Al11Si alloy and...
Article
Full-text available
In general, many cast parts require a final surface finish which could be sand blasting, grinding, or machining. In such applications, the cutting tool life is a critical parameter where the mass production rate becomes important. Therefore, in this work, the correlation between melt quality and machin- ability of the high-pressure die-cast Al9Si3C...
Article
Full-text available
Aluminium and its alloys are the most commonly used alloys in the transportation sector due to their high lightness and strength ratio. The higher corrosion resistance increases the reason why this alloy is preferred. In order to increase the strength values to the desired levels, aluminium alloys are subjected to grain refining with Ti, solution h...
Chapter
Metal matrix compositesMetal Matrix Composite with fiber reinforcement elements have a high potential to improve properties such as mechanical strength and elastic behavior. Therefore, the development of fiber-reinforced aluminumAluminum alloys provides an opportunity for increased use in the automotive, aerospace, and aerospace fields. In this stu...
Chapter
The requirement for lightweight in automotive and aerospace applications has been the focal point in many studies. Lately, the effect of rare-earth element addition to Al–Si alloys has begun to be investigated in detail. The aim is to establish higher tensile properties with new alloying element additions. In this work, different ratios of Er, Eu,...
Article
Aluminum alloys are widely used in industry due to their lightness and ease of machining. Concurrently, the mechanical properties of aluminum alloys can be increased by different development studies. Grain refining, modification and heat treatment can be given as examples of these development studies. In this study, the influences that may occur in...
Article
In this work, porosity formation with regard to the change in the metallostatic pressure was investigated. Different geometry was generated to simulate the effect of pressure on critical solid fraction. A380 alloy was sand cast. Additionally, the effect of grain refiner and modifiers was also investigated. Samples were subjected to X-ray radiograph...
Article
The demand for lighter weight decreased thickness and higher strength has become the focal point in the automotive industry. In order to meet such requirements, the addition of several alloying elements has been started to be investigated. In this work, the additions of V, B, and Sr on feedability and tensile properties of A360 has been studied. A...
Presentation
Full-text available
Optimization of the desired process parameters can be realized by modeling the production processes. In this study, it is aimed to investigate the effect of cold rolling and annealing process on the 1050, 3005, 3105, 8006 aluminum commercial alloys produced by twin roll casting. Cold rolling process were applied at different deformation rates betwe...
Article
Full-text available
Strontium master alloy is widely used in today's aluminum foundries for modification of Al-Si alloys. In this study, Al-Sr master alloy was produced in molten Al alloy directly from strontium carbonate instead of using the pure strontium metal which is difficult to store in the air due to its high oxygen affinity. In a laboratory-scale induction fu...
Article
Full-text available
This study aimed to determine the optimal casting parameters for the maximum fluidity of A356 alloy. Gravity die cast method was used. For this purpose, central composite design (CCD) was performed. The input parameters and their limits for the trial design were selected as pre-heating temperature (100-400°C), casting temperature (680-760°C), and c...
Article
Full-text available
The microstructure of Al-Si alloy has coarse silicon and this structure is known dangerous for mechanical properties due to its crack effect. Sr addition is preferred to modify the coarse silica during solidification. Additionally, bifilms (oxide structure) are known as a more dangerous defect which is frequently seen in light alloys. It is aimed a...
Article
Optimization of casting parameters is essential in terms of quality factors in foundries. Nowadays, to optimize process parameters, new approaches such as artificial neural networks method are being used. In this study, a neural network model has been developed to control the grain size in aluminum casting alloys. Some of the important grain refine...
Article
This study has investigated the effect of different amounts of Cr and Zr additions on the microstructure and mechanical properties of A356 alloy modified with strontium. The microstructure and phase examination were performed using an optical microscope, scanning electron microscope and XRD analysis, whereas mechanical properties were investigated...
Article
Full-text available
In this study, the effects of different mold types and quenching mediums with different internal stresses on the mechanical properties of ETIAL 221 alloy supplied as a primer were investigated, and analyzed statistically. Firstly, the alloy was poured into the permanent mold (PM) then poured into sand mold with grain size 40/45 and 60/65 AFS. The s...
Article
The use of boron carbide-reinforced aluminium matrix composites has grown rapidly in critical applications of aerospace industries, automotive sectors, military, and nuclear engineering. However, boron carbide reinforcement within AA6061 alloy is worthy of investigation in terms of its mechanical and tribological properties. Novel aluminium matrix...
Article
Full-text available
Strontium modification of Al–Si alloys has known to have several beneficial effects such as increased feedability, the formation of fibrous Si and increased mechanical properties. However, in the presence of Sr, during melting and holding durations, the oxide structure of the dross may change which leads to several problems during casting operation...
Chapter
Full-text available
In this study, numerical modelling was applied in order to determine the conductivity values of AA1050, AA3005, AA3104, and AA3105 alloys after different thermomechanical processes. Conductivity difference contour plot graphs of aluminum were performed with different thermomechanical processes. Samples were taken from AA1050, AA3005, AA3104, and AA...
Article
Full-text available
Aluminium and its alloys have been widely used in the automotive industry for some time and A356 is one of the most popular aluminium alloys today in the sector. It contains approximately 7 wt.% Si and 0.3 wt.% Mg. Due to the defects that may be present in the cast parts, expected mechanical properties may not be reached and this alloy may perform...
Article
Aluminium matrix composites (AMCs) have great potential for critical applications within aerospace, automotive, defence, marine, agriculture and nuclear engineering sectors. The composite materials are very attractive because of their good balance between lightweight versus high strength and machinability. Depending on the particular application, t...
Article
The relation between time-dependent corrosion behaviors and microstructural characteristics of Sr modified and unmodified AlSi9 alloy was studied. The melted alloys were cast into the permanent mold at 700 °C casting temperature. The Effect of holding time in the furnace on chemical compositions of alloys was determined. Sr content of the modified...
Article
In this study, different melt treatment operations were evaluated and compared to end product’s scrap rate using bifilm index (BI) method. Results clearly show that degassing with finer gas bubbles increases cleaning performance for the removal of any type of bifilms in the melt. BI method is a reliable and quick way to determine melt quality at an...
Chapter
Full-text available
Al-Si alloys are widely preferred in the casting industry due to their superior properties. When the coarse silicones are modified, the silicon structure is homogeneously dispersed and higher mechanical properties are achieved. Despite the continuous use of the modification process, there are uncertain points about the working mechanism. A full und...
Chapter
The aim of this study is to investigate the effects of cryogenic process (CP) on the properties of 2024-T6 aluminum alloy. So, samples were held at −40 °C medium for 24 h in CP after solution heat treatment. Finally, samples were subjected to aging process at 120 °C for 8 h after CP. Furthermore, aging process was carried out after 0, 1, and 4 h la...
Chapter
In this study, changes in mechanical properties and hot tearing properties were investigated by adding 0.2 wt% Ni and 2 wt% Cu to Al–Si–Mg alloy. In addition, the porosity formation with regard to liquid metal cleanliness was investigated. Casting experiments have been carried out in certain compositions. The melt was degassed and up-gassed slowly....
Article
In this study, it aimed to produce carbon fiber (CF) reinforced aluminum metal matrix composite by squeeze casting method. In order to overcome the wetting problem between the aluminum matrix and the reinforcing agent, carbon fibers were coated with Ni coating with electroless technique. Different bath pH values and hypophosphite (HP), coating dura...
Chapter
This study aims to investigate how casting quality change in aluminum melt during the holding period in liquid state. 10 kg of ingot was melted in a SiC crucible by using an electrical furnace. A sample was taken every five minutes from 0 to 55 min after the alloy was melted. Reduced pressure test (RPT) samples were collected to be solidified under...
Chapter
Full-text available
Degassing operations are common methods to remove inclusions and oxides from the melt. In many occasions, fluxes are used through the melt in order to increase efficiency of oxide removal. In this work, a dirty melt was prepared by means of adding 50 wt% swarf to primary A356 alloy. Fluxes with various ratios of NaCl–KCl and MgCl 2 –KCl salts were...
Chapter
In this study, due to the enhanced properties of graphene, it was aimed to produce aluminum matrix composite by graphene reinforcement. Several different methods were applied such as lost foam casting, sand casting, die casting, ceramic mold casting and squeeze casting. The incorporation of the graphene was established by only squeeze casting metho...
Chapter
Investigation of the fracture surface is an effective method in characterizing casting defects. Some data can be collected such as the population of defects and initiation of fracture by means of investigation of fracture surface via a scanning electron microscope (SEM). In this study, tensile test samples from two different 356 aluminium melts tha...
Chapter
Global strategy for material science in the automotive industry is to use the lightweight material. In the present work, the casting of aluminum alloy with high magnesium content has been performed with the addition of B, Sr, Ti and Zr. Gravity sand casting and permanent mold casting methods were used. Microstructural evolution has been studied alo...
Chapter
Grain refinement of cast alloys provides several advantages such as establishment of finer dendritic structure, lowered porosity due to increased feeding, and thereby higher mechanical properties are reached. For Al–Si alloys, Ti is the preferred; however, Ti has the tendency to sink to the bottom of the crucible due to density difference. In this...
Chapter
It is known that vanadium and boron elements are used as grain refiners. In this study, it was aimed to increase the mechanical properties of A356 by grain refinement. Boron and vanadium elements were added in an amount of 0.05 wt% and 0.1 wt%. Al–10 V and Al–3B master alloys were used. The melts were casted into sand and permanent molds at 730 °C....
Chapter
Al8Si3Cu alloy was studied to investigate the effect of casting conditions on melt quality of the molten metal. While Sr and Ti master alloys were used as additional parameters, holding time was performed for effect of held liquid. Experimental study was tried before and after degassing. The reduced pressure test machine was used to produce samples...
Chapter
High-pressure die casting is the most suitable method for mass production of Al–Si alloys. The cast parts are typically subjected to machining for the final finish. In this work, the cutting tool life was investigated with regard to the melt quality. The melt cleanliness is defined by reduced pressure test and bifilm index was measured. Since bifil...
Chapter
Strontium modification has many advantages for the mechanical properties of Al–Si alloys. Holding time is an important factor in Sr modification. Its high affinity to oxygen may result in forming of SrO. Al 2 O 3 spinel oxides. Therefore, Sr quantity in the melt can decrease by time due to fading. In this work, this phenomenon was investigated in A...
Chapter
In this study, the deep etch method was applied to Al–Si casting alloys in order to visualize the presence of the bifilms. Reduced pressure test was used to quantify the bifilms in the melt. The cross section of the RPT samples was subjected to deep etching with H 2 SO 4 , HNO 3 , NaOH, and NaCl solutions at various temperatures and concentrations....
Article
Full-text available
In this work, commercially available Al-7Si alloy was used, and the microstructure was modified by the additions of AlSr15, AlTi5B1, and Al3B. Cylindrical samples were cast into a sand mold and the machinability of the alloys was characterized by means of surface roughness, chip morphology, and buildup edge of the chips. Tool life and surface finis...
Conference Paper
Full-text available
Al-Si alloys are commonly used in automotive and aerospace industries. The control of the internal structure in the parts produced by the casting method is very important. With the change of the internal structure, different features can be achieved. Generally, the microstructure is tried to be modified by the addition of alloying elements to the l...
Conference Paper
Full-text available
The attention on composite material increases day by day. Because of their mechanical properties, composite materials have taken the place of heavy industrial material as well as aluminum. This study focuses on aluminum metal matrix composites (AMMC) produced by mechanical stirring supported with ultrasonic stirring application. Silicon carbide (Si...
Conference Paper
The aim of this study was to investigate the effect of different stirring methods on the mechanical properties of aluminum matrix composite in comparison with applied and computer aided simulations. In experimental applications, A356 alloy was used as matrix material and SiC (50-56 μm, 1wt%) was used as reinforcement material. As stirring methods;...
Conference Paper
Al-Si alloys are the most preferred alloys for gravity and high pressure casting. Solid solubility of iron in aluminum is less than 0.05% in equilibrium. Thus, almost all of the iron in the aluminum alloys forms the second phase particles. Fe intermetallics occur due to the limited resolution of aluminum and steel systems. As the Fe level increases...
Article
Full-text available
Corrosion behavior of A356 aluminum alloy with different grain refiners was evaluated. For this purpose, the Sr-modified A356 alloy was grain refined with Al5Ti1B and Al3B, and then, the corrosion characteristics were determined. For the mechanical properties, impact and Vickers hardness tests were carried out. To determine the corrosion behavior,...
Conference Paper
Full-text available
In many of the casting operations, whether an ERP (Enterprise Resource Planning) is installed or not, there is a good control of process parameters. The melting temperature is measured, degassing operation is always repeated at the same parameters, runner and sprue design is made and pouring is carried out in the same controlled manner. Although ea...
Conference Paper
Full-text available
The usage of secondary aluminum has a large volume in the industry due to the economic beneficial. The effect of degassing on the melt quality, microstructure and mechanical properties of secondary alloys were studied in this article. Fluidity and melt quality are have a important roles on mold filling. Fluidity was examined with new-design mold an...
Conference Paper
For comparison the effects of the domestic sr-master alloy and commercial master alloy additions on the microstructure and mechanical properties of strontium (Sr) on Al-9Si-0.3Mg alloy were investigated in the present work. Microstructure was examined with optical microscope (OM) and SEM-EDS. Hardness and UTS tests were performed. Analysis of mean...
Article
Full-text available
In most of the practical casting operations, it is important to be able to cast large number of part with one single melt. Therefore, when quantity of the charge and melting crucible is increased, during casting process, the liquid is led to settle for a long period of time. In this work, 10 kg charge of A356 was melted at 750 °C and held for 240 m...
Article
The aim of this study was to investigate the effect of different stirring methods on the mechanical properties of aluminum matrix composites in association with applied and computer-aided simulations. Four kilograms of A356 aluminum alloy was used as the matrix material, and 1 wt% silicon carbide (SiC) with an average particle size of 50–56 μm was...
Article
Full-text available
A homogeneous equiaxed grain structure is necessary for semisolid forming of aluminum alloys. One of the methods used to obtain such microstructure is strain induced melt activated process. The aim of this work is to optimize the heat treatment parameters for extruded 7075 alloy required to obtain the spheroidal grain structure suitable for thixofo...
Article
Full-text available
Light weight, low density with high mechanical properties and corrosion resistance, aluminum is the most important material and is commonly used for high performance applications such as aerospace, military and especially automotive industries. The researchers who participate in these industries are working hard to further decrease the weight of en...
Article
3XX series Al–Si alloys are generally used in corrosive environments open for oxidation such as rainwater and seawater. The dendrite size and characteristics of the eutectic Si are important factors determining the properties of A356 alloy. In this study, the microstructure of Sr modified A356 aluminum alloy and the changes in corrosion properties...
Conference Paper
Full-text available
In this study, hardness development of Al7Si0,3Mg alloy according to DAS, SDAS and phase ratios were investigated. The mold in which the castings are carried out was a cascaded mold and specimens with variable wall thicknesses of 20 mm, 10 mm and 5 mm were produced. The casting temperature 750°C and the mold temperature was chosen 400°C. Images of...
Article
Full-text available
Bu çalışma, hurda A356 alüminyum alaşımının sıvı metal kalitesi arttırılarak mekanik özelliklerin geliştirilmesi aynı zamanda ikincil alüminyum kullanımını artırmak amacıyla yapılmıştır. Tamamen döndü yani %100 ikincil alüminyumdan 5kg’lık şarj hazırlanmıştır. Ultrasonik gaz giderme işlemi 750°C’de 60, 120 ve 180 sn olmak üzere üç farklı sürede uyg...
Conference Paper
Full-text available
Al-Si alloys are mostly used in casting industry for automotive parts. In this alloy, silicon need to be modified to obtain fine fibrous particles instead of coarse needles. Strontium master alloys have been used as modifier in Al-Si alloys for decades [1,2]. The modification was first discovered in 1921 by Aladar Pacz and his unique method was pat...
Conference Paper
Full-text available
İkincil alüminyumun, şekilli parça üretimine geri kazandırılmasının önemi; artan alüminyum talebi ve mevcut alüminyum kaynakları düşünüldüğünde günümüzde çalışılması gereken bir konu haline gelmiştir. [1] Yapılan çalışmalarda, ikincil alüminyumun kalitesinin arttırılması için, kimyasal katkı (eritken) ve gaz (Ar,N2) kullanılmaksızın, yüksek frekans...
Article
Full-text available
In this work, macrostructure, microstructure and deformation hardness of as-cast and austempered ductile iron chips produced by different cutting speeds were investigated. Cutting forces, surface roughness and tool wear were also studied. After austenitizing at 900 ºC for 90 min, ferritic and pearlitic ductile iron specimens were austempered in a s...
Article
The oxide layer on liquid aluminum serves as a protective property to prevent the alloy from further oxidation. However, it has the potential to be a source of porosity when entrained into the bulk of the liquid. For this reason, oxides entrained into aluminum castings have been shown to degrade casting quality. In the current study, the effectiven...
Article
Full-text available
Hot tearing tendency of A380 with various element additions (Sr, Sr+Ti, Ti, B and B+Sr) was investigated. Constrained rod casting (CRC) hot tearing test method was used to characterize the hot tearing sensitivity. Reduced pressure test (RPT) samples were produced from each condition and all trials were repeated three times. Number density of pores...
Article
In this study, three different aluminum-silicon alloys (A356, A413, and A380) that have different solidification morphology and solidification ranges were examined with an aim to evaluate the hot tearing susceptibility. T-shape mold and Constrained Rod Casting (CRC) mold were used for the characterization. Reduced Pressure Test (RPT) was used to qu...
Article
Al-4.5Cu alloys are widely used in aerospace industries due to their low weight and high mechanical properties. This group of aluminium alloys is known as 2xx series and exhibits the highest mechanical properties however this alloy is known to suffer from feedability and high tendency for hot tearing. Al-Si alloys (3xx) have improved fluidity and b...
Article
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Aluminium alloys are one of the preferred materials especially for land and air transportation because of their high strength and low-density properties. Although production using casting method is economical yet it has some disadvantages. Shrinkage which is occurred due to the density difference between the solid and liquid metal is prevented by f...
Article
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Carbon nanotube (CNT) and ceramic nanoparticles have different effects on the mechanical properties in epoxy nanocomposites. There are several mechanisms that explain how the differences for mechanical properties in these two different reinforcement are. In this study, multi-walled CNT and three different ceramic nanoparticles (Fe2O3, SiO2 and Al2O...
Article
Full-text available
In this work, T-shaped mould design was used to generate hot spot and the effect of Sr and B on the hot tearing susceptibility of A356 was investigated. The die temperature was kept at 250°C and the pouring was carried out at 740°C. The amonut of Sr and B additions were 30 and 10 ppm, respectively. One of the most important defects that may exist i...
Article
Full-text available
Grain refining and modification are common foundry practice for improving properties of cast Al-Si alloys. In general, these types of treatments provide better fluidity, decreased porosity, higher yield strength and ductility. However, in practice, there are still some discrepancies on the reproducibility of the results from grain refining and effe...
Article
The effect of melt quality on hot tearing susceptibility of Al8Si3Cu alloy was examined under six different conditions, by using a traditional T-shaped mold. Grain refinement was carried out by two different modifiers: AlTi5B1 and Al3B. For each test, samples were cast before and after degassing of melt. Therefore, a new hot tearing tendency index...
Conference Paper
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In this study, multi-walled CNT and three different ceramic nanoparticles (Fe2O3, SiO2 and Al2O3) reinforcements on tensile properties of epoxy were examined. The weight percent of these additions were kept to be 0.5 wt% in all the tests. Tensile tests were carried out in order to characterize the mechanical properties.It was found that all the add...
Poster
Full-text available
Mühendislik malzemelerinde artan kaliteli ürün talebi sürekli olarak mevcuttaki malzemelerin geliştirilmesi ya da yeni malzemelerin ortaya çıkarılması zorunluluğunu doğurmuştur. Bu çalışmada da en yaygın şekilde kullanılan alüminyum alaşımlarından biri olan Al7Si0,3Mg birincil (cevher) ve ikincil (hurda) alaşımlarının titreşimli dökümü yapılarak ta...