Dursun ÖZYÜREK, Tansel TUNÇAY, Süleyman TEKELİ

DİFÜZÖRLÜ VE DİFÜZÖRSÜZ YOLLUK SİSTEMLERİNİN A356 ALAŞIMININ MEKANİK ÖZELLİKLERİNE ETKİSİ

Bu çalışmada, A356 alüminyum döküm alaşımında eşit kesit alanına ve farklı kesit şekillerine sahip difüzörlü ve difüzörsüz yatay yolluk sistemlerinin, sıvı metal hareketine bağlı olarak mekanik özellikleri üzerine etkisi incelenmiştir. Çalışmanın amacı, yolluk sistemlerinin sebep olduğu inklüzyon, gaz veya çekme boşluğu gibi döküm hatalarını azaltmaktır. Bu yüzden yatay yolluklar, eşit kesit alanına ve farklı kesit şekline sahip (kare, dikdörtgen ve dairesel çıkışlı) difüzörler kullanılarak genişletilmiştir. Dökülen A356 alaşımı plakalardan hazırlanan numunelerden çekme testleri yapılarak, elde edilen sonuçlar Weibull istatistiksel analizi ile incelenmiştir. Yapılan çalışmalar sonucunda, tasarlanan difüzörlü yatay yolluklarda sıvı metalin hareketindeki türbülansın azaldığı en yüksek çekme değerleri ve Weibull modülünün kare kesitli difüzörlü yatay yolluk kullanılarak dökülen numunelerde olduğu görülmüştür. Kırık yüzey Tarama Elektron Mikroskobu (SEM) incelemelerinde ise kırılmanın, intermetalik ikincil fazların (oksitlerin vb.) ve boşlukların bulunduğu bölgelerde gerçekleştiği gözlenmiştir.

THE EFFECT OF DIFFUSER AND NON-DIFFUSER RUNNER SYSTEMS ON THE MECHANICAL PROPERTIES OF A356 ALLOY

In this study, runner systems which have equal cross-sectional area and different forms of cross-sectional diffuser and non-diffuser runner system s effects on mechanical properties of A356 aluminium alloy, depending on the movement of the liquid metal, were investigated. The aim of the study is to reduce casting defects due to inclusion caused by runner systems such as gas or shrinkage porosity. Therefore, the horizontal runners have been extended by using diffusers having cross-sectional area equivalent with a different cross-sectional shape (square, rectangular and circular outlet). Tensile test specimens were prepared from the plates of casting A356 alloy and tensile tests were performed. Obtained results were examined Weibull statistical analysis. As a result, one hand, it is observed that the turbulence effect on liquid metal has been decreased the highest tensile results and Weibull modulus has been appeared on the samples which have horizontal runners produced by using a square section diffuser in designed horizontal diffuser. On the other hand, according to Scanning Electron Microscope (SEM) analysis on fracture surfaces, fracture has been observed in the area of intermetallic secondary phases (oxides etc.) and in area with gas or shrinkage porosity.

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