The Investigation of the Effects of T6 and High Temperature Pre-precipitation HTPP Heat Treatments on Hot Tensile Properties of AA7075 Aluminium Alloys

Year 2020, Volume: 12 Issue: 2, 683 - 692, 30.06.2020

Talha Sunar Dursun Özyürek

https://doi.org/10.29137/umagd.718364

Abstract

Mechanical properties at elevated temperatures for AA7075 aluminium alloy processed with two different heat treatment as T6 and HTPP, were investigated in this study. The alteration in strength and hardness which can be occur as a result of heat treatment was aimed to research. For this purpose, tensile tests were carried out at the temperatures of 100, 200, 300⁰C. The microstructures of the samples which tensile tests were applied, examined by optical microscope and scanning electron microscope SEM. As results for the studies made, it was observed that T6 samples showed better strength properties but HTPP samples has better ductility properties with respect to T6 samples. For the hardness results, higher hardness values were obtained from T6 samples. Fracture surfaces examinations showed that the fracture was semi-ductile for the temperatures below 200⁰C and ductile for the temperatures of 200 and 300⁰C. It is determined that the ductility was increased with the rise in the temperature.

Keywords

AA7075 alloy, ageing, hardness, microstructure, hot tensile

T6 ve Yüksek Sıcaklık Ön-Çökeltme HTPP Isıl İşleminin AA7075 Alüminyum Alaşımının Yüksek Sıcaklıktaki Çekme Özelliklerine Etkilerinin İncelenmesi

Abstract

Bu çalışmada, T6 ve HTTP olmak üzere iki farklı yaşlandırma ısıl işlem uygulanmış AA7075 alaşımının yüksek sıcaklık mekanik özellikleri incelenmiştir. Isıl işlemler ile alaşımın dayanımında ve sertliklerinde meydana gelen değişimlerin araştırılması amaçlanmıştır. Bu nedenle, 100, 200 ve 300⁰C sıcaklıklarda çekme testleri gerçekleştirilmiştir. Çekme testleri yapılan numunelerin mikroyapıları optik mikroskop ve taramalı elektron mikroskobu (SEM), X-ışını kırınımı (XRD) ve sertlik ölçümleri ile incelenmiştir. Yapılan çalışmalar sonucunda, T6 yaşlandırma ısıl işlemi uygulanan numunelerin, HTPP uygulanan numunelere göre daha iyi dayanım özellikleri gösterdikleri fakat HTPP numunelerinin süneklik özelliklerinin T6’ya göre daha iyi olduğu gözlemlenmiştir. Sertlik sonuçları için de T6 uygulanan alaşımdan daha yüksek sertlik değeri sonuçları elde edilmiştir. Kırılma yüzeyleri incelemeleri 200⁰C altında yarı-sünek bir kırılma ve 200 ve 300⁰C sıcaklıklarda sünek kırılma olduğunu göstermektedir. Sünekliğin artan sıcaklıkla birlikte arttığı belirlenmiştir.

Keywords

AA7075 alaşımı, yaşlandırma, sertlik

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