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

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

Günümüzde artan kalite talepleri nedeniyle geleneksel yöntemlerle üretilen malzemeler istenilen özelliklere sahip olamamaktadır. Kaliteli malzeme üretmek için, malzemenin iç yapısının homojen ve safsızlıklardan arınmış olması gerekmektedir. İçyapıyı türdeş hale getirebilmek ve malzemedeki safsızlıkların giderilebilmesi için eritken (flaks), gaz giderme, vs. gibi hem kimyevi hem de mekanik ya da her ikisinin de birlikte kullanıldığı birçok sıvı metal işlemi uygulanmaktadır [1], [2]. Sıvı metalin safsızlıklardan giderilmesi için uygulanan işlemlere ilaveten nihai döküm parçasının titreşimli döküm gibi yöntemler ile yüksek mukavemetli malzemelerin üretilmesi de mümkündür. Katılaşma sırasında metale uygulanan titreşimin tane yapısını değiştirdiği ve birincil dendrit kollarını (DAS) kısaltıp, ikincil dendrit kolları arasındaki mesafeyi (SDAS) kısalttığı bilinmektedir. Çalışmada %100 birincil A356 alaşımı farklı genlikde uygulanan titreşim etkisi altında katılaştırılmıştır. Uygulanan titreşim dalgalarının karakterinin malzeme yapısı üzerindeki etkilerini incelemek amacı ile farklı genliklerde (7,5, 5 ve 2,5 cm) titreşim uygulanarak katılaştırılan numuneler metalografik olarak incelenmiş, DAS, SDAS ve faz oranları hesaplanarak karşılaştırılmıştır.

International Symposium on Light Alloys and Composite Materials
UHAKS

Çağlar Yüksel Ahmet Kabil Muhammet Cemal Öztürk Hüseyincan Eker Eray Erzi Derya Dışpınar