SÜRTÜNME KARIŞTIRMA KAYNAĞI İLE BİRLEŞTİRİLMİŞ BAĞLANTILARDA PİM ÇAKIŞMASININ MEKANİK ÖZELLİKLER ÜZERİNE ETKİSİ

Bu çalışmada, AA-7075 T651 alüminyum alaşımlı plakaların sabit bir pim ofset mesafesi ve iki farklı ofset yönü ile üst üste bindirilmiş iki kaynak dikişi için mekanik özelliklerindeki değişimler araştırılmıştır. Herhangi bir ofset olmaksızın plakaların temas yüzeyinde gerçekleştirilen tek kaynak dikişinin mekanik özellikleri ile karşılaştırma yapılmıştır. Ayrıca kaynaklı bağlantılar için mikroyapısal incelemeler yapılarak kaynaklı bağlantılardaki kusurlar ve pim karıştırma bölgesine ait tane yapısındaki değişimler araştırılmıştır. Deneysel verilerin değerlendirilmesi sonucunda en yüksek çekme mukavemeti olan 423 MPa, 400 dev/dak takım dönme hızında ve herhangi bir çakışmanın olmadığı tek kaynak dikişine sahip kaynaklı bağlantıdan elde edilmiştir. Bu koşul için ölçülen birim uzama %10 iken, en yüksek birim uzama değeri %12,5, 400 dev/dak ve pim ofset yönü olarak pimin dönüş yönünün seçildiği kaynaklı bağlantıdan elde edilmiştir. En yüksek mukavemet ve birim uzama (%) değeri üç farklı pim ofset yönü için de takım dönme hızının 400 dev/dak olduğu durumda elde edilmiştir. Takım dönme hızındaki artış ile çekme dayanımında ve birim uzama (%) değerinde azalma meydana geldiği ortaya çıkmıştır.

Anahtar Kelimeler:

Sürtünme karıştırma kaynağı, pim çakışması, mekanik özellikler, mikroyapı

EFFECT OF PIN OVERLAP ON MECHANICAL PROPERTIES OF FRICTION STIR WELDED JOINTS

In this study, the changes in mechanical properties of AA-7075 T651 aluminum alloy plates for a fixed pin offset distance and two overlapping weld seams with two different offset directions were investigated. Comparisons were made with the mechanical properties of the single weld seam formed on the contact surface of the plates without any offset. In addition, microstructural observations of welded joints were carried out to investigate the defects in welded joints and the changes of grain structure in the nugget zone. As a result of evaluation of the experimental data, the highest tensile strength, 423 MPa, was obtained from the welded joint with single weld seam which was manufactured with a tool rotational speed of 400 rpm and without any pin overlap. The elongation at rupture for this condition was measured to be 10%, while the highest elongation at rupture, 12.5%, was obtained from the joint welded with a tool rotational speed of 400 rpm and where AS was selected as the pin offset direction. The highest strength and elongation at rupture (%) for all three different pin offset directions were obtained with the tool rotational speed of 400 rpm. It was revealed that with the increase in tool rotational speed, both tensile strength and elongation at rupture (%) decreased.

Keywords:

Friction stir welding, pin overlap, mechanical properties, microstructure,

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