SEARCH RESULT

In practice, ceramic foam filters are generally used in aluminium sand and die casting processes in order to decrease number of defects. Efficiency of filters depend on the pore size. Ardekhani and Raiszadeh [1] claim that 30 ppi filters can eliminate almost all of bifilms from molten aluminium but filters will decrease cleanliness of molten metal because of creating new surfaces. Bozchaloei et al. [2] indicate that it is important that it is important where the filter is placed in mould cavity. Also, efficiency of filtration is more than 65% to increase mechanical properties of casting parts [1, 3].

International Symposium on Light Alloys and Composite Materials
UHAKS

Özen Gürsoy2 Eray Erzi Cekdar Vakıfahmetoğlu Gian Domenico Soraru Derya Dışpınar

Improved mechanical properties in Al-Si alloys can be achieved by Sr modification. In the present study, the addition of Sr is carried out by Al-15wt%Sr master alloy where the total quantitiy of Sr in the alloy is preferred to be around 300 ppm. Since melt quality is significantly affected by bifilms which are folded oxide layers, the influence of Sr modification in A360 alloy over holding time of the melt has been evaluated. Reduced pressure test was used to assess melt quality. Microstructural analysis was carried out. Sample collection was made at 4 th and 17th hours of holding time and it was found that both Sr modification and bifilm index were decreased over time. It was also seen that Sr content decreases significantly with increasing holding time. Tensile test specimens were also prepared in order to observe the effects of modification and different casting conditions on the mechanical properties of A360 alloy. Aluminium-silicon based alloys are widely used especially due to their good mechanical properties, corrosion resistance and castability, for light weight components in automotive and aerospace industries where it is used for cylinder blocks and heads and plain bearings [1-3]. The mechanical properties of Al-Si alloys depend significantly on the morphology of eutectic silicon. Modification is one of the most important melt treatments for aluminium- silicon alloys castings. Desired properties of Al-Si alloys can be achieved by modification in two diferrent ways, either by rapid cooling rate or by addition of certain modifier elements, such as Sr or Na [2,3]. Both elements cause multiplication of twins and coraline-like microstructure. However, Na has a high tendency to fade because of high volatility. Therefore, Sr is a good alternative to Na [4]. The eutectic silicon phase crystallizes into a coarse, plate- like morphology during eutectic formation. This coarse morphology of eutectic silicon is disadvantageous for the casting. With modification the morphology of eutectic is changed from coarse, birttle flakes which leads to poor mechanical properties to finer and fibrous structure [4-5].

International Symposium on Light Alloys and Composite Materials
UHAKS

Inal Kaan Duygun Özen Gürsoy2 Eray Erzi Derya Dışpınar

Aluminium alloys widely used because of its high rate of strength/density, good electrical conductivity and high corrosion resistance in automotive and aerospace industries. In recent years, Al-matrix fiber composites have studied and investigated due to increasing strength and decreasing density. In this study, carbon fibers were coated with electroless Ni to investigate composite fiber production conditions with 6063 aluminium alloy. Nickel-coated fibers produced in different thicknesses depending on the coating conditions such as temperature, pH, and time were used in the production of Al-matrix fiber composite using squeeze casting method.

International Symposium on Light Alloys and Composite Materials
UHAKS

Gökçe H. Ağaoğlu Anıl Alten Özen Gürsoy2 Eray Erzi Derya Dışpınar Gökhan Orhan

A356 aluminium alloy is most commonly used and researched casting alloy in the aerospace and automotive industries. In practice, A356 is casted basically two different moulds: die and sand. If it’s necessary to compare, it has been claimed that much higher mechanical properties are obtained by using die mould in casting. It is known that a similar effect is observed by using Al-Ti-B grain refiner master alloy [1-3]. Microstructural differences have been shown as the main reason of this. In this study, the relation between microstructure and mechanical properties was investigated. The effects of bifilm, cooling rate and grain refinement factors on the relation were observed. Secondary 356 aluminium alloy was melted at 725 ºC and Al-5Ti-1B master alloy was used as grain refiner at addition ratio of 0.1%. Samples of tensile test and stair (for microstructure analyses depend on different cooling rate) were poured at die and sand moulds. RPT samples were produced to determine bifilm index. Data were evaluated in Weibull statistical analyses.

International Symposium on Light Alloys and Composite Materials
UHAKS

Özen Gürsoy2 Eray Erzi Derya Dışpınar

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 patented. In the Pacz study, it has been shown that Al-Si alloys with Si content of 5-15% are modified with alkali fluoride, preferably sodium fluoride fluxes. Closset and Gruzleski, have shown that strontium can be used as a modifier in silicon-containing alloys [1].

International Symposium on Light Alloys and Composite Materials
UHAKS

Ibrahim Goksel Hizli Rasit Sezer Özen Gürsoy2 Selim Ertürk Cüneyt Arslan Derya Dışpınar

Degassing process is widely used in aluminium casting process to clean the liquid aluminium (decrease the bifilm index) with various diffusors as it can be seen at Figure 1 Degassing process reduces non-metallic inclusions (such as bifilm) since they generally become attached to the rising bubble and are subsequently skimmed from the surface. Also, inert gas bubbles bring about excellent stirring that assist in homogenising the temperature and chemical composition of the melt.

International Symposium on Light Alloys and Composite Materials
UHAKS

Emrah Duran Furkan Karasoy Gülistan Kara Özen Gürsoy2 Eray Erzi Derya Dışpınar

Strontium modification of Al-Si alloys has many advantages for the casting parts. Particularly, mechanical properties are increased and castability of the alloy is improved. However, Sr has high affinity to oxygen and it may form SrO. Al2O3 spinel oxides on the surface of the melt depending on the holding time of the liquid. Thus, Sr quantity in the melt can decrease by time. In this work, this phenomenon was investigated in A413 alloy. The melt was held at 700°C and 750°C for 4 and 17 hours. Metallographic examination was carried out for the Sr fading effect measurement. In addition, melt quality change was recorded by means of bifilm index change. Even low additions of Sr results in favorable changes in the quality of casting by affecting the nucleation and crystallization mechanisms. It was proved that Sr levels in tha range between 100 ppm and 400 ppm is enough for coarse, flaky eutectic phase to be transformed finer fiberous morphology [1] However it is proposed that even 50 ppm of Sr can change the morphology efficiently [2] Besides that the fading effect which is because of the increasing holding time at high temperatures and varying treatment times may also affect the efficiency of Sr on the modification of Al-Si alloys [3]. Another important factor which changes the melt quality is the oxide-flms which can remain suspended in melts for a long periods. During casting, these oxide-films may fold double and cause cracks after solidification [4]. In this work the effect of holding time on modification was investigated by comparing modified and unmodified alloys at 700°C and 750°C. Reduced pressure test was also used to assess changing metal quality by measuring the Bifilm indices of samples.

International Symposium on Light Alloys and Composite Materials
UHAKS

Inal Kaan Duygun Özen Gürsoy2 Eray Erzi Derya Dışpınar

Titanium is widely preferred in clinical medicine and dentistry because of mechanical properties, high corrosion resistance and biocompatibility. Ti reacts with oxygen in the air to form a stable thin film of TiO2. The TiO2 layer protects Ti from corrosion. However, this layer gets unstable when Ti material is exposed to reducing environment and corrosion can occur. Ti surface can be modified with acids. Surface topography of implants in dental applications is quite important for osseointegration. Modified surface of dental implant increases, osseointegration enhances, and so length of treatment period of patients gets shorter in applications. Surface modification can be performed by many methods such as sandblasting-acid etching (SLA), plasma spraying, coating etc. SLA is most performed technic in all of these. However, most recent studies have shown that sandblasting process before etching could endanger health of patient because of leaving residues in SLA process. So, studies have focused on acid etch modification without sandblasting. HCl, H2SO4, HF, HNO3 etc. are some of the acids used in the process. In this study, the effect of etching with different acid concentrations and with different time on the surface morphology of Ti6Al4V (Grade 5) alloy was investigated. For this purpose, two different experimental study were carried out. In the first one, sulfuric acid (H2SO4) solution was prepared at different concentrations: 48, 60, 75 and 95% for Ti6Al4V alloy plate samples with dimensions of 10x10x2 mm3. The samples were treated with H2SO4 concentrations for different durations: 30, 60, 180 min. at the room temperature in order to comparing the etching effect. The initial and final weights of the samples were measured and the weight change per unit area (Ϫ) was calculated. Surfaces of untreated samples and treated samples with the highest Ϫ value for each concentration were examined by scanning electron microscopy (SEM). The chemical composition of the alloy is shown in Table 1 In the second one, H2SO4 solution was prepared at concentration of 48% for Ti6Al4V alloy cylindrical samples with dimensions of π x 32 x 20 mm3. These samples were treated with concentration of 48% H2SO4 solution for different durations: 30, 60, 90 and 180 minutes at the room temperature and 60°C in order to comparing the etching effect. However, was not calculated for second step of the experimental study, Ϫ values were not calculated but whole samples were examined by SEM.

International Symposium on Light Alloys and Composite Materials
UHAKS

Özen Gürsoy2 Gökçen Erdem A. Günay Bulutsuz Çiğdem Mercan Ezgi Tan A. Bülent Katiboğlu Gökçe H. Ağaoğlu Gökhan Orhan Derya Dışpınar