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Öğe A Statistical Assessment of Casting Quality-Tribological Properties of Eutectic Al-12Si Alloy: Effect of Mg(Springer, 2020) Uludağ, MuhammetThis work was carried out to evaluate the relationship between casting quality and wear properties of Al-12Si eutectic alloy with various Mg contents. Mg additions were selected as 0, 2, 3, and 4 wt.%. A permanent die tensile test mold, step-type mold, and RPT sand mold were used in the characterization of the properties of the castings. The bifilm index was measured for the determination of the casting quality. Mechanical properties such as hardness, UTS, YS, e (%), toughness, impact, and wear rate were investigated. All the results obtained in this study were evaluated via statistical analysis software. It was found that melt quality and bifilm index is the dominant factor that determines the mechanical properties. As Mg content was increased, the size of oxides was getting smaller and their number was increased. The highest wear properties were obtained with the highest Mg addition (4 wt.%) for ball-on-disk tests. According to the pin-on-disk test, in the lubricated conditions, there was no change in wear properties with Mg content. In the dry tests, as the bifilm index was increased, the friction coefficient was decreased due to the higher oxide content of the alloy.Öğe Change in Porosity of A356 by Holding Time and Its Effect on Mechanical Properties(Springer, 2018) Uludağ, Muhammet; Cetin, Remzi; Gemi, Lokman; Dispinar, DeryaIn 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, 10kg charge of A356 was melted at 750 degrees C and held for 240min. A sand mold with different thickness was cast at 30, 60, 120, and 240min of holding time of the liquid, before and after degassing conditions. Melt quality was measured by reduced pressure test, and pore size and number were measured at each cast part. A correlation between bifilm index and tensile properties was established. It was found that melt quality was decreased with increased holding time and pore formation was enhanced linearly. Additionally, mechanical properties of the alloy were decreased with decreased melt quality and increased pore formation due to holding time of the liquid.Öğe Characterization of the Effect of Melt Treatments on Melt Quality in Al-7wt %Si-Mg Alloys(Mdpi Ag, 2017) Uludağ, Muhammet; Cetin, Remzi; Dispinar, Derya; Tiryakioglu, MuratThe effects of degassing, holding time and melt additions (Sr, Sr + Ti, Ti, B and B + Sr) on the quality of A356 melts were examined. A total of 120 reduced pressure test samples were collected. Pores in these samples were analyzed via digital image processing to determine the number density of pores as well as the statistical distribution of their sizes. Results showed that in all cases, degassing with argon reduced the number of defects regardless of the additions made to the melts. Moreover, all additions were found to degrade melt quality. The lowest number density of pores in all melts was achieved in melts with no additions that were degassed. In both degassed and non-degassed melts, Sr additions degraded the melt quality significantly. The mechanisms of melt quality improvement or degradation with different melt treatments are discussed in the paper.Öğe Characterization of the effect of Sr and Ti on liquid quality in Al8Si3Cu(Springer International Publishing, 2019) Uludağ, Muhammet; Dispinar, D.; Tiryakioğlu, M.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 which are five samples for each parameter. Samples were prepared by metallographic methods to be analyzed with via digital image processing. Pores on the surface of the samples were measured in number density and distribution of them was examined statistically. Results showed that while Sr addition and holding time increased casting defects by increasing porosity, degassing decreased the number density of defects, as expected. Therefore, it is a vital result that degassing process must be applied to every casting. In addition, Ti addition was found to have a slight positive effect to reduce porosity, but it was almost negligible when compared to that of degassing process. © The Minerals, Metals & Materials Society 2019.Öğe EFFECT OF DEGASSING AND GRAIN REFINEMENT ON HOT TEARING TENDENCY IN Al8Si3Cu ALLOY(Springer International Publishing Ag, 2018) Uludağ, Muhammet; Cetin, Remzi; Dispinar, Derya; Tiryakioglu, MuratThe 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 was developed by both bifilm calculations and porosity that occurred in the middle of T-zone of casting parts. Results indicated that hot tearing of cast aluminum alloys was a complex phenomenon, and bifilms play a major role, especially by compensating for shrinkage and consequently contributing to the inconsistencies in results.Öğe Effect of quenching mediums on mechanical properties of Al-Cu alloy(Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association, 2018) Uludağ, Muhammet; Gurtaran, M.; Dispinar, D.[No abstract available]Öğe Effect of Ti addition holding time on casting quality and mechanical properties of A356 alloy(Springer International Publishing Ag, 2020) Gurtaran, Mikdat; Uludağ, MuhammetBifilms are casting defects that occur due to the incorporation of surface oxide film into the melt. Thus, they act as a crack in the liquid. Once they remain in the structure, they decrease mechanical properties owing to their negative effect on porosity formation. One of the most fundamental problems to be avoided in this frame is the reduction of the bifilms or the cleaning of the liquid metal to prevent the porosity formation. In this study, A356 (Al-7Si-0.3 Mg) alloy was used. AlTi5B1 master alloy was added as a grain refiner. The effect of Ti on casting quality and mechanical properties changes by holding time was evaluated. The results were examined statistically by Weibull analysis. It was found that the presence of bifilms can be reduced as holding time increases after adding Ti. The tensile properties were increased as the holding time increased. Additionally, the optimum holding time may be 40 min after Ti addition for high casting quality and good mechanical properties.Öğe Efficiency of Ti addition in A356 alloy under different holding time(Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association, 2018) Uludağ, Muhammet; Gurtaran, M.; Dispinar, D.[No abstract available]Öğe Experimental and Statistical Analysis of Effect of Si Modification and Grain Refinement on Tensile Properties of A356 Alloy(Gazi Universitesi, 2021) Uludağ, MuhammetThe focus point of recent research on light metal castings has been on the effect of casting quality on the material properties and maximizing the quality is the most important factor toward obtaining the best properties from an alloy. Sr additions modify Si morphology while grain refiners such as AlTixBy and Ti-free B make dendrite arms smaller in the alloy. Therefore, this study has been performed to evaluate the relationship between casting quality and tensile properties of A356 alloy. The modification and refinement treatments were carried out with three different master alloys: AlSr15, AlTi5B1, and AlB3. The tests were conducted under two conditions: with and without degassing to evaluate the effect of change in melt quality. Results obtained from experimental studies were analyzed statistically. It was concluded that there is a good relationship between bifilm index and tensile test results when the bifilm index is divided into three groups, namely: poor, medium and high quality. It was found that while Ti grain refinement addition positively affects the mechanical properties, Sr addition has a negative effect on casting quality.Öğe Experimental and statistical analysis of low velocity impact response of filament wound composite pipes(Elsevier Sci Ltd, 2018) Gemi, Lokman; Kayrici, Mehmet; Uludağ, Muhammet; Gemi, Dilek Soylu; Sahin, Omer SinanNowadays, filament wound composite pipes (GRP) are used as a structural element in many applications such as natural gas and oil transmission lines, and portable bridge constructions for military purposes. GRP pipes can expose to impact loading from various causes. This loading can cause an invisible level of damage. Thus, the detection and evaluation of such damages are of great importance. In this study, the low velocity impact response of (+/- 55 degrees)(3) filament wound E-glass/epoxy composite pipes has been studied. The pipes have been subjected to drop weight impact loading with various impact energies. The force-time and force-displacement relations have been examined. The impact damage formation was also evaluated. It is concluded that the damage development in the pipes is controlled by displacement trough radial direction. The obtained results were evaluated statistically by means of Weibull approach. Microscopy analysis of impacted region revealed that debonding, radial cracks, transfer cracks and delamination damage modes are the main observed damage modes.Öğe Freezing Range, Melt Quality, and Hot Tearing in Al-Si Alloys(Springer, 2018) Uludağ, Muhammet; Cetin, Remzi; Dispinar, DeryaIn 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 quantify the casting quality by measuring bifilm index. It was found that bifilm index and solidification range have an important role on the hot tearing formation. As it is known, bifilms can cause porosity and in this case, it was shown that porosity formed by bifilms decreased hot tearing tendency. As the freezing range of alloy increases, bifilms find the time to unravel that reduces hot tearing. However, for eutectic alloy (A413), due to zero freezing range, regardless of bifilm content, hot tearing was never observed. A380.1 alloy had the highest tendency for hot tearing due to having the highest freezing range among the alloys investigated in this work.Öğe Influence of Al-B grain refiner on porosity formation of directionally solidified Al-Si alloys(Springer Singapore Pte Ltd, 2020) Uludağ, MuhammetThis work aims to present a perspective for porosity formation in three different alloys: A356, A413 and A380.1 by taking into account the addition of Al-B grain refiners: AlTi(5)B(1)and Al3B. The directional solidification method was used, and microstructural changes of the alloys and its correlation with porosity formation were investigated. Pore size, number of pores, average pore length and distribution of pores were statistically analyzed. Also, external shrinkage was examined, and the volume of external shrinkage was calculated. It was found that there was a relationship between external shrinkage and the size and number of pores. As the size and number of pores internally decrease, external shrinkage increases. Additionally, porosity is decreased in all the three Al-Si alloys when Al-B grain refiners are used. The distribution of pore diameters is low when AlTi(5)B(1)is used. Grain refiners have a different effect on porosity formation of Al-Si alloys with regard to their solidification morphology.Öğe Investigation of casting quality change of A356 by duration in liquid state(Springer International Publishing, 2019) Uludağ, Muhammet; Gurtaran, M.; Dispinar, D.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 80 mbar. All samples were sectioned into two parts vertically, and one of them was prepared for metallographic examination. Surface of the samples was subjected to image analysis by using via image analysis software. Bifilm index and bifilm area were analyzed in detail. As a result, it can be concluded that first 30 min of liquid metal is important, because casting quality tends to get worse after 30 min. © The Minerals, Metals & Materials Society 2019.Öğe Investigation of the efficiency of grain refiners on the hot tearing in Al8Si3Cu alloy(Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association, 2018) Uludağ, Muhammet; Çetin, R.; Dispinar, D.[No abstract available]Öğe Observation of Hot Tearing in Sr-B Modified A356 Alloy(Polska Akad Nauk, Polish Acad Sciences, 2017) Uludağ, Muhammet; Cetin, R.; Dispinar, D.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 degrees C and the pouring was carried out at 740 degrees C. The amonut of Sr and B additions were 30 and 10 ppm, respectively. One of the most important defects that may exist in cast aluminium is the presence of bifilms. Bifilms can form by the surface turbulence of liquid metal. During such an action, two unbonded surfaces of oxides fold over each other which act as a crack. Therefore, this defect cause many problems in the cast part. In this work, it was found that bifilms have significant effect over the hot tearing of A356 alloy. When the alloy solidifies direetionally, the structure consists of elongated dendritic structure. In the absence of equiaxed dendrites, the growing tips of the dendrites pushed the bifilms to open up and unravel. Thus, leading to enlarged surface of oxide to become more harmful. In this case, it was found that these bifilms initiate hot tearing.Öğe ON THE INTERPRETATION OF MELT QUALITY ASSESSMENT OF A356 ALUMINUM ALLOY BY THE REDUCED PRESSURE TEST: THE BIFILM INDEX AND ITS PHYSICAL MEANING(Springer International Publishing Ag, 2018) Uludağ, Muhammet; Cetin, Remzi; Dispinar, Derya; Tiryakioglu, MuratThe 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 effectiveness of the reduced pressure test in assessing the quality of A356 alloy melts has been investigated under various conditions obtained by changing six different melt parameters. Several metrics, including average pore size, number density of pores, bifilm index, have been used to measure melt quality. Results have shown that the bifilm index provides reliable measurements of melt quality. Moreover, the bifilm index has been found to have a physical meaning, volume fraction of pores, especially when bifilm index is higher than 50 mm.Öğe Relationship Between Machinability, Microstructure, and Mechanical Properties of Al-7Si Alloy(Amer Soc Testing Materials, 2018) Uludağ, Muhammet; Yazman, Sakir; Gemi, Lokman; Bakircioglu, Baris; Erzi, Eray; Dispinar, DeryaIn 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 finish can be improved by decreased chip size by lowering the energy required for machining. The surface finish is an indicator of the quality of the material during the machining process. Therefore, in addition, melt quality was measured by means of reduced pressure test and the calculation of the bifilm index was used to compare the melt quality with machinability. It was found that there is a good correlation between bifilm index and surface roughness of the machined parts. Thus, for a better surface finish, melt quality, which can be quantified by bifilm index, has to be high. AlSr15 modified alloy exhibits the lowest built-up edge with the lowest surface roughness, because strontium modification causes coarse silicon crystals to transform to fine fibrous structure, which enhances machinability.Öğe STATISTICAL ANALYSIS ON THE EFFECT OF THE SOLIDIFICATION RATE AND QUENCHING MEDIUMS ON MECHANICAL PROPERTIES IN ETIAL 221 ALLOY(2020) Uludağ, Muhammet; Gemı, Lokman; Dispinar, DeryaIn 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 specimens were subjected to three different T6 heat treatment quenching mediums that are water at room temperature (WRT), oil (OL) and boiling water (BW). The influences of differences in solidification rate due to cooling rates and differences in internal stress due to quenching mediums on mechanical properties were investigated. Additionally, the change in porosity was calculated according to Archimedes principle and obtained results were related to the mechanical properties. The results showed that permanent mold and boiling water quenching medium presented the best mechanical properties for the current study.Öğe The Effect of Bifilm and Sr Modification on the Mechanical Properties of AlSi12Fe Alloy(Polska Akad Nauk, Polish Acad Sciences, 2020) Uludağ, Muhammet; Gurtaran, M.; Dispinar, D.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 at that negative effect of bifilms on the properties of the alloys tried to be removed by the degassing process and to regulate the microstructure of the alloy. In this study, the effect of degassing and Sr modification on the mechanical properties of AlSi12Fe alloy was investigated, extensively. Four different parameters (as-received, as-received + degassing, Sr addition, Sr addition + degassing) were studied under the same conditions environmentally. The microstructural analyses and mechanical tests were done on cast parts. All data obtained from the experimental study were analyzed statistically by using statistical analysis software. It was concluded from the results that Sr addition is very dangerous for AlSi12Fe alloy. It can be suggested that to reach high mechanical properties and low casting defects, the degassing process must be applied to all castings whereas Sr addition should not be preferred.Öğe The effect of SR modification and Ti grain refinement on the mechanical properties of A356(Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association, 2018) Uludağ, Muhammet; Dispinar, D.[No abstract available]
