CMT ve Darbeli CMT Ark Kaynaklı AA7075-T6 AlAlaşımı Alın Bağlantıların Mekanik Davranışına Kaynak Hatalarının Etkisinin Araştırılması

Al-alaşımları hafiflik, iyi korozyon performansı, iyi şekillendirilebilirlik ve yüksek mukavemet gibioldukça iyi bir mekanik özellik kombinasyonuna sahiptir. Bunun sonucu, özellikle de hafiflik istenen taşımacılıksanayi başta olmak üzere birçok alanda yaygın olarak kullanılmaktadırlar. Ancak, bu alaşımların, özellikle deyaşlandırma sertleşmesi yapılmış AA7075-T6 gibi yüksek mukavemetli olan türlerinin, ergitme kaynağındaporozite oluşumu, çatlama ve kaynak bölgesinde aşırı mukavemet kaybı gibi problemlerle karşılaşılmaktadır.Dolayısıyla, bu alaşımların başarılı bir şekilde kaynaklanabilir olması endüstride daha da yaygın olarakkullanılmalarını sağlayacaktır. Bu bağlamda, katı hal kaynakları ve soğuk metal transferi (cold metal transfer –CMT) gaz metal ark kaynağı (GMAK) veya lazer kaynağı gibi düşük ısı girdili ergitme kaynakları ümitvadetmektedir.Bu çalışmanın amacı, soğuk metal transferi (CMT) ark kaynağı tekniği kullanılarak kaynak edilenAA7075-T6 levhaların kaynak dikişinde porozite oluşumu ve oluşan porozitenin kaynaklı levhanın mekaniközelliklerine etkisinin incelenmesidir. Bu çerçevede, 2 mm kalınlığındaki AA7075-T6 Al-alaşımı levhalar hemgeleneksel CMT hem de darbeli CMT ark kaynağı yöntemleri kullanılarak birleştirilmiştir. Kaynaklı levhalarıniçyapıları ve mekanik özellikleri detaylı optik mikroskop çalışmaları, mikrosertlik ölçümleri ve çekme deneyi ileincelenmiştir. Ayrıca, kaynak dikişinde oluşan iri porozitelerin kaynaklı levhanın mekanik davranışına etkisinibelirlemek için porozite oluşumu ile kaynak performansı arasında bir ilişki kurulmaya çalışılmıştır.

Investigation of the Influence of Weld Defects on the Mechanical Behavior of Cold Metal Transfer (CMT) and Cold Metal Transfer Pulsed (CMT-Pulsed) Arc Welded AA7075-T6 Al-Alloy Butt Joints

Al-alloys possess a very good combination of mechanical properties such as lightweight, good corrosion performance, good formability and high strength. Thus, they are widely employed in several industries, particularly in transport industry, where lightweight is required. However, fusion joining of these alloys, particularly age hardened grades such as AA7075-T6, involve several difficulties such as porosity formation, cracking and loss of strength in the weld area. Thus, successful joining of these alloys will further increase their use in industrial applications. In this respect, solid state joining or fusion welding techniques with low heat input such as cold metal transfer (CMT) gas metal arc welding (GMAW) technique or laser beam welding are promising joining methods. This study aims at investigating the formation of weld defects (i.e., pores) and determining the effect of pores on mechanical performance of the AA7075-T6 plate joints produced using CMT arc welding technique. For this purpose, AA7075-T6 Al-alloy plates with a thickness of 2 mm were joined using both conventional CMT and CMT pulse arc welding techniques. The microstructural and mechanical properties of the welded plates were investigated by detailed optical microscopy investigations, micro-hardness measurements and tensile tests. Moreover, a correlation between the joint performance and the formation of porosity in the fusion zone (FZ) was also attempted to show the effect of the presence of large pores on the mechanical behavior of the joint.

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