Musa BİLGİN, Şener KARABULUT, AHMET ÖZDEMİR

AA7075-T6 ve AZ31B Alaşımlarının Sürtünme Karıştırma Kaynağı Üzerinde Ön Isıtma ve Kuru Buz Soğutmasının Etkisi

Bu çalışmada, AA7075T6 alüminyum ve AZ31B magnezyum alaşımlarının sürtünme karıştırma kaynak (SKK) yöntemi ile kaynak edilebilme özelliği araştırılmıştır. Farklı kimyasal ve mekanik özelliklere sahip alüminyum ve magnezyum alaşımlarını sürtünme karıştırma kaynağı ile birleştirebilmek için sabit devir, sabit tabla ilerleme hızı, farklı takım kaydırma değerlerinde, numunelere ön ısıtma ve kuru buz ile soğutma işlemleri uygulanarak dört farklı kaynak işlemi yapılmıştır. Birleştirilmiş numunelerin kaynak kalitesi, tahribatlı ve tahribatsız muayene yöntemleri kullanılarak değerlendirilmiştir. Alüminyum alaşımına uygulanan ön ısıtmanın ve kaynak işlemi sırasında uygulanan kuru buz ile soğutmanın mekanik ve mikro yapısal özellikler üzerindeki etkisi incelenmiştir. Test sonuçları, önceden ısıtılmış ve kaynak işlemi sırasında kuru buz ile soğutulmuş kaynaklı numunelerinin çekme dayanımının daha yüksek olduğunu göstermiştir. Ön ısıtma işlemine tabi tutulmuş numunelerin kaynak yüzeyinde gözenek oluşumu görülürken, kuru buz ile soğutma yapılarak birleştirilen numunenin kaynak hattında boşluk oluşumu gözlenmiştir. Normal kaynaklı numunelere kıyasla, ön ısıtma ve kuru buz soğutma işlemine tabi tutularak birleştirilmiş numunelerin karıştırma bölgesinde homojen bir karışım elde edilmiştir.

Anahtar Kelimeler:

AA7075, AZ31B, sürtünme karıştırma kaynağı, ön ısıtma, kuru buz soğutma, mekanik özellikler, mikro yapı

Effect of Preheating and Dry Ice Cooling on Dissimilar Friction Stir Welding of AA7075-T6 and AZ31B

In this study, dissimilar friction stir welding behavior of AA7075-T6 aluminum and AZ31B magnesium alloys were investigated. Aluminum and magnesium alloys were joined by friction stir welding under four welding conditions and in two environments, namely pre-heated aluminum and dry ice for cooling, with tool rotation of 1120 rpm, table speed of 20 mm/min and two different tool offset values. The welding quality of the joined specimens were evaluated by employing destructive and non-destructive testing methods. The influence of the pre-heating applied to the aluminum alloy and employing ice cooling during the welding process on the mechanical and microstructural properties were examined. The test results showed that the higher tensile strength values were obtained from welded specimens of the pre-heated and cooled by dry ice during the welding process. Porosities were seen on the welded surface of the pre-heated specimen while the cavities were observed on the joint line of the cooled specimen using dry ice during the process. A homogenous material mixing was achieved in the stir zone of the welded specimens subjected to pre-heating and dry ice cooling process compared with the normal welded specimens.

Keywords:

AA7075, AZ31B, friction stir welding, pre-heating, dry ice cooling, mechanical properties, microstructure,

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