INVESTIGATION OF MICROSTRUCTURAL AND HARDNESS CHANGES OF AA7075 ALLOY PROCESSED BY ECAP

Abstract

This study aims to examine the change in microstructural and hardness values AA7075 aluminum alloy, which is frequently preferred in the aviation industry by applying the Equal Channel Angular Pressing (ECAP) method. ECAP method, one of the plastic deformation methods, has been successfully carried out by applying 0.025mm/sec pressing speed and 200°C temperature for a different route (A, Bc, C) and the different number of passes (2, 4, 8). The characterization of the aluminum alloy obtained by applying ECAP process was carried out by optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) analysis. Hardness tests have been applied to examine the mechanical properties of the material. The microstructures of the materials obtained as a result of the application were examined. It was observed that precipitation occurred in the AA7075 alloy depending on the applied temperature, pressing, and grain breakage. Moreover, it is seen that the grain size of the materials produced by the ECAP method has been reduced, and consequently the strength of the material increases. As a result of the ECAP process, it was seen that the existing phases were α-Al, -MgZn2, S-Al2CuMg, and Al7Cu2Fe. The grain size of 288.4 nm obtained after 8 repeated passes using the Bc route was the smallest grain size obtained.

Keywords

• Severe Plastic Deformation
• Equal Channel Angular Pressing (ECAP)
• Al-Zn-Mg Alloy
• Microstructure
• Hardness

ECAP UYGULANAN AA7075 ALAŞIMININ MİKRO YAPI VE SERTLİK DEĞİŞİMLERİNİN İNCELENMESİ

Abstract

Bu çalışmada, havacılık endüstrisinde sıklıkla tercih edilen AA7075 alüminyum alaşımına EKAP uygulanarak alaşımın mikroyapısal ve sertlik değerlerindeki değişimin incelenmesi amaçlanmıştır. Plastik deformasyon yöntemlerinden biri olan EKAP yöntemi, farklı rota (A, Bc, C) ve farklı paso sayıları (2, 4, 8) için 0,025mm/sn presleme hızında ve 200°C’de başarıyla uygulanarak gerçekleştirilmiştir. EKAP işlemi uygulanarak elde edilen alüminyum alaşımının karakterizasyonu optik mikroskop (OM), X ışını kırınımı (XRD) ve taramalı elektron mikroskobu (SEM) analizleri ile yapılmıştır. Malzemenin mekanik özelliklerinin incelenebilmesi için sertlik testleri uygulanmıştır. Uygulama sonucunda elde edilen malzemelerin mikroyapıları incelenmiştir. AA7075 alaşımında uygulanan sıcaklık, presleme ve tane kırılmasına bağlı olarak çökelmenin meydana geldiği görülmüştür. Ayrıca ECAP yöntemi ile üretilen malzemelerin tane boyutunun küçültüldüğü ve buna bağlı olarak malzemenin mukavemetinin arttığı görülmektedir. EKAP işlemi sonucunda mevcut fazların α-Al, -MgZn2, S-Al2CuMg ve Al7Cu2Fe olduğu görülmüştür. Bc rotası kullanılarak 8 tekrarlı geçiş sonrasında elde edilen 288.4 nm tane boyutu elde edilen en küçük tane boyutu olmuştur.

Keywords

• Aşırı Plastik Deformasyon
• Eş Kanallı Açısal Presleme
• Al-Zn-Mg Alaşımı
• Mikroyapı
• Sertlik

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