Effect of welding travel speed and post-weld artificial aging on the mechanical and microstructural properties of friction stir welded AA6063-T6 aluminum alloy

Öz

In this study, the effects of varying welding travel speeds and post-weld artificial aging treatment on the microstructural evolution and mechanical properties of AA6063-T6 aluminum alloy joints produced by friction stir welding were investigated. The joints were fabricated using a constant tool rotational speed and three different travel speeds, followed by a post-weld artificial aging treatment applied under a controlled atmosphere. Characterization of the welded joints was performed using tensile tests, microhardness mapping, optical microscopy, and scanning electron microscopy analyses. In the as-welded specimens, a distinct softening behavior in the heat-affected zone and a characteristic W-shaped hardness profile were observed, attributed to the dissolution or coarsening of strengthening precipitates induced by the welding thermal cycle. Conversely, the post-weld artificial aging treatment facilitated the reprecipitation of fine and dense Mg₂Si phases within the matrix, thereby homogenizing the hardness distribution and significantly enhancing mechanical performance. Notably, the specimens welded at a travel speed of 300 mm/min and subsequently aged exhibited strength values superior to those of the base metal, achieving a joint efficiency of 108.8%. It was observed that the increase in strength was accompanied by a slight reduction in ductility, and the fracture mechanism shifted from a ductile mode to a mixed fracture mode featuring shallower dimples. In conclusion, this study demonstrates that the softening problem typically encountered in friction stir welding can be largely mitigated through the optimization of welding parameters combined with an appropriate artificial aging treatment, enabling the production of joints with properties superior to those of the base metal.

Anahtar Kelimeler

• Friction stir welding
• artificial aging
• mechanical properties
• microstructure
• precipitation hardening

Destekleyen Kurum

Çuhadaroğlu Metal Sanayi ve Pazarlama A.Ş.

Proje Numarası

AGTMPR140083

Etik Beyan

We declare that this study is an original work; that scientific ethical principles and rules were followed during all stages of the study, including preparation, data collection, analysis, and presentation of information; that all data and information not obtained within the scope of this study have been cited and included in the references; that no alterations were made to the data used; and that the study adheres to all ethical duties and responsibilities by accepting all terms and conditions of the Committee on Publication Ethics (COPE). We acknowledge that we will accept all moral and legal consequences that may arise if any violation of this declaration is detected at any time.

Teşekkür

This study was carried out within the scope of the project conducted at the Çuhadaroğlu Metal Sanayi ve Pazarlama A.Ş. R&D Center, under the project code AGTMPR140083.

Sürtünme karıştırma kaynağı ile birleştirilen AA6063-T6 alüminyum alaşımlarında kaynak ilerleme hızı ve kaynak sonrası yapay yaşlandırmanın mekanik ve mikroyapısal özelliklere etkisi

Öz

Bu çalışmada sürtünme karıştırma kaynağı yöntemiyle birleştirilen AA6063-T6 alüminyum alaşımlarında farklı kaynak ilerleme hızlarının ve kaynak sonrası yapay yaşlandırma işleminin mikroyapısal dönüşüm ve mekanik özellikler üzerindeki etkileri incelenmiştir. Deneysel süreçte sabit takım dönme hızı ve üç farklı ilerleme hızı kullanılarak birleştirmeler gerçekleştirilmiş ve ardından numunelere kontrollü atmosfer altında yapay yaşlandırma işlemi uygulanmıştır. Birleştirmelerin karakterizasyonu amacıyla çekme testleri ve mikrosertlik haritalamaları ile optik ve taramalı elektron mikroskobu analizleri yapılmıştır. Kaynak durumundaki numunelerde termal döngü etkisiyle güçlendirici çökeltilerin çözünmesi veya kabalaşması sonucu ısıdan etkilenmiş bölgede belirgin bir yumuşama davranışı ve karakteristik W şeklinde sertlik profili tespit edilmiştir. Buna karşın kaynak sonrası uygulanan yapay yaşlandırma işlemi ile matris içerisinde ince ve yoğun Mg₂Si fazının yeniden çökelmesi sağlanarak sertlik dağılımı homojen hale getirilmiş ve mekanik performans önemli ölçüde iyileştirilmiştir. Özellikle 300 mm/dk ilerleme hızı ile üretilen ve yaşlandırılan numunelerde ana metalden daha yüksek mukavemet değerleri elde edilerek %108,8'lik bir kaynak verimliliğine ulaşılmıştır. Mukavemet artışına paralel olarak süneklikte bir miktar azalma meydana geldiği ve kırılma davranışının sünek moddan daha sığ oyukçuklar içeren karma bir karaktere dönüştüğü gözlemlenmiştir. Sonuç olarak kaynak parametrelerinin optimizasyonu ve uygun yaşlandırma işlemi kombinasyonu ile sürtünme karıştırma kaynağında karşılaşılan yumuşama sorununun yüksek oranda giderilebileceği ve ana metalden daha üstün özelliklere sahip birleştirmelerin üretilebileceği ortaya konulmuştur.

Anahtar Kelimeler

• Sürtünme karıştırma kaynağı
• yapay yaşlandırma
• mekanik özellikler
• mikroyapı
• çökelti sertleşmesi

Destekleyen Kurum

Çuhadaroğlu Metal Sanayi ve Pazarlama A.Ş.

Proje Numarası

AGTMPR140083

Etik Beyan

Bu çalışmanın, özgün bir çalışma olduğunu; çalışmanın hazırlık, veri toplama, analiz ve bilgilerin sunumu olmak üzere tüm aşamalarından bilimsel etik ilke ve kurallarına uygun davranıldığını; bu çalışma kapsamında elde edilmeyen tüm veri ve bilgiler için kaynak gösterildiğini ve bu kaynaklara kaynakçada yer verildiğini; kullanılan verilerde herhangi bir değişiklik yapılmadığını, çalışmanın Committee on Publication Ethics (COPE)' in tüm şartlarını ve koşullarını kabul ederek etik görev ve sorumluluklara riayet edildiğini beyan ederiz. Herhangi bir zamanda, çalışmayla ilgili gerçekleştirilen bu beyana aykırı bir durumun saptanması durumunda, ortaya çıkacak tüm ahlaki ve hukuki sonuçlara razı olduğumuzu bildiririz.

Teşekkür

Bu çalışma, Çuhadaroğlu Metal Sanayi ve Pazarlama A.Ş. Ar-Ge Merkezi bünyesinde, AGTMPR140083 proje kodu ile yürütülen proje kapsamında gerçekleştirilmiştir.

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