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

References

• Acer, E., Çadirli, E., Erol, H., Kirindi, T. & Gündüz, M. (2016). Effect of heat treatment on the microstructures and mechanical properties of Al-5.5Zn-2.5Mg alloy. Materials Science and Engineering A, 662,144–156.
• Andreatta, F., Terryn, H. & De Wit J. H. W. (2004). Corrosion behaviour of different tempers of AA7075 aluminium alloy. Electrochimica Acta, 49 (17–18), 2851–2862.
• Berg, L. K., Gjønnes, J., Hansen, V., Li, X. Z., Knutson-Wedel, M., Schryvers, D., & Wallenberg, L. R. (2001). GP-zones in Al–Zn–Mg alloys and their role in artificial aging. Acta materialia, 49(17), 3443-3451.
• Cassada, W., Liu, J. & Staley, J. (2002). Aluminum alloys for aircraft structures. Advanced Materials And Processes, 160 (12), 27–29.
• Chinh, N. Q., Lendvai, J., Ping, D. H. & Hono, K. (2004). The effect of Cu on mechanical and precipitation properties of Al–Zn–Mg alloys. Journal of Alloys and Compounds, 378(1-2), 52-60.
• Cina, B. M. (1974). Unitet States Patent. Patent Number: 3,856,584.
• Deschamps, A., Bréchet, Y., Guyot, P. & Livet, F. (1997). On the influence of dislocations on precipitation in an Al-Zn-Mg alloy. Zeitschrift Fuer Metallkunde/Materials Research and Advanced Techniques, 88 (8), 601–606.
• Donald O. S. (1994). United States Patent. Patent Number: 3,198,676.
• Fakioglu, A., Özyürek, D. & Yilmaz, R. (2013). Effects of different heat treatment conditions on fatigue behavior of AA7075 alloy. High Temperature Materials and Processes, 32 (4), 345–351.
• Ferrer, C. P., Koul, M. G., Connolly, B. J. & Moran, A. L. (2003). Improvements in strength and stress corrosion cracking properties in aluminum alloy 7075 via low-temperature retrogression and re-aging heat treatments. Corrosion, 59 (6): 520–528.
• Guo, Y., Zhou, M., Sun, X., Qian, L., Li, L., Xie, Y., Liu, Z., Wu, D., Yang, L., Wu, T., Zhao, D., Wang, J., & Zhao, H. (2018). Effects of temperature and strain rate on the fracture behaviors of an Al-Zn-Mg-Cu alloy. Materials, 11 (7), 1–15.
• Hatch, J. E. (1984). Aluminum: properties and physical metallurgy. Metals Park, Ohio: American Society for Metals,
• Huang, L. P., Chen, K. H., Li, S. & Song, M., (2007). Influence of high-temperature pre-precipitation on local corrosion behaviors of Al-Zn-Mg alloy. Scripta Materialia, 56 (4), 305–308.
• Huang, L., Chen, K., & Li, S. (2012). Influence of grain-boundary pre-precipitation and corrosion characteristics of inter-granular phases on corrosion behaviors of an Al-Zn-Mg-Cu alloy. Materials Science And Engineering B: Solid-State Materials For Advanced Technology, 177 (11), 862–868.
• Iwaszko, J. & Kudła, K. (2020). Surface remelting treatment of 7075 aluminum alloy — microstructural and technological aspects. Materials Research Express, 7(1): 016523
• Jung, S. H., Lee, J. & Kawasaki, M. (2018). Effects of pre-strain on the aging behavior of Al 7075 alloy for hot-stamping capability. Metals, 8 (2):137.
• Kalyon, A., & Özyürek, D. (2017). Investigation of the effect of different heat treatments on wear behavior of AA7075 Alloy. Acta Physica Polonica A, 131 (1), 150–152.
• Kim, S. W., Kim, D. Y., Kim, W. G. & Woo, K. D. (2001). The study on characteristics of heat treatment of the direct squeeze cast 7075 wrought Al alloy. Materials Science and Engineering A, 304–306 (1–2), 721–726.
• Kobayashi, T. (2000). Strength and fracture of aluminum alloys. Materials Science And Engineering A, 286 (2), 333–341.
• Li, J. F., Peng, Z. W., Li, C. X., Jia, Z. Q., Chen, W. J. & Zheng, Z. Q. (2008). Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments. Transactions of Nonferrous Metals Society of China, 18(4), 755-762.
• Liu, D., Atkinson, H. V., Kapranos, P., Jirattiticharoean, W. & Jones, H. (2003). Microstructural evolution and tensile mechanical properties of thixoformed high performance aluminium alloys. Materials Science and Engineering A, 361 (1–2), 213–224.
• Liu, G., Zhang, G. J., Ding, X. D. Sun, J. & Chen, K. H. (2003). Dependence of fracture toughness on multiscale second phase particles in high strength Al alloys. Materials Science and Technology, 19 (7), 887–896.
• Ma, K., Wen, H., Hu, T., Topping, T. D., Isheim, D., Seidman, D. N., Lavernia, E. J. & Schoenung, J. M. (2014). Mechanical behavior and strengthening mechanisms in ultrafine grain precipitation-strengthened aluminum alloy. Acta Materialia, 62 (1), 141–155.
• Maire, E., Zhou, S., Adrien, J. & Dimichiel, M., (2011). Damage quantification in aluminium alloys using in situ tensile tests in X-ray tomography. Engineering Fracture Mechanics, 78 (15), 2679–2690.
• Malarvizhi, S. & Balasubramanian, V. (2011). Effect of welding processes on AA2219 aluminium alloy joint properties. Transactions Of Nonferrous Metals Society Of China (English Edition), 21 (5), 962–973.
• Marlaud, T., Deschamps, A., Bley, F., Lefebvre, W., & Baroux, B. (2010). Influence of alloy composition and heat treatment on precipitate composition in Al-Zn-Mg-Cu alloys. Acta Materialia, 58 (1), 248–260.
• Melvin, H. B., (1943). Unitet States Patent. Patent Number: 4,477,292.
• Mouritz, A. P. (2012). Introduction to Aerospace Materials. Cambridge, England: Woodhead Publishing Ltd.
• Ozer G., & Karaaslan A. (2017). Properties of AA7075 aluminum alloy in aging and retrogression and reaging process. Transactions of Nonferrous Metals Society Of China (English Edition), 27 (11), 2357–2362.
• Pahlavani, M., Marzbanrad, J., Rahmatabadi, D., Hashemi, R. & Bayati, A. (2019). A comprehensive study on the effect of heat treatment on the fracture behaviors and structural properties of Mg-Li alloys using RSM. Materials Research Express, 6(7), 076554.
• Park, S. Y., & W. J. Kim. (2017). Enhanced Hot Workability and Post-Hot Deformation Microstructure of the As-Cast Al-Zn-Cu-Mg Alloy Fabricated by Use of a High-Frequency Electromagnetic Casting with Electromagnetic Stirring. Metallurgical and Materials Transactions A, 48(7), 3523-3539.
• Rahman, A. M., Sirajudeen, N. & Patnaik, S. (2018). Effect of different heat treatments and varying volume fraction of nano Al2O3 particles on the hardness and wear resistance of Al 7150 alloy matrix composite synthesized by hot uniaxial compaction technique. Materials Research Express, 6(8), 086515.
• Rao, A. C. U., Vasu, V., Govındaraju, M. & Srınadh, K. V. S., (2016). Stress corrosion cracking behaviour of 7xxx aluminum alloys: A literature review. Transactions Of Nonferrous Metals Society Of China (English Edition), 26 (6), 1447–1471.
• Rometsch, P. A., Zhang, Y. & Knight, S. (2014). Heat treatment of 7xxx series aluminium alloys - Some recent developments. Transactions Of Nonferrous Metals Society Of China (English Edition), 24 (7), 2003–2017.
• Rout, P. K., Ghosh, M. M. & Ghosh, K. S. (2015). Microstructural, mechanical and electrochemical behaviour of a 7017 Al-Zn-Mg alloy of different tempers. Materials Characterization, 104,49–60.
• Shojaei, K., Sajadifar, S. V., & Yapici, G. G. (2016). On the mechanical behavior of cold deformed aluminum 7075 alloy at elevated temperatures. Materials Science and Engineering A, 670,81–89
• Şimşek, İ., Şimşek, D., Özyürek, D. & Tekeli, S. (2019). The effect of the aging time on microstructure and mechanical properties of the AA7075 alloy after T6 heat treatment. Metallofiz. Noveishie Tekhnol, 41(6), 817-824.
• Song, M. & Chen, K. (2008). Effects of the enhanced heat treatment on the mechanical properties and stress corrosion behavior of an Al-Zn-Mg alloy. Journal of Materials Science, 43 (15), 5265–5273.
• Standard, A. S. T. M. (2009). ASTM E21–09: standard test method for elevated temperature tension tests of metallic materials. ASTM International, West Conshohocken, PA.
• Standard, A. S. T. M., E3-11. (2011). Standard guide for preparation of metallographic specimens. ASTM International, West Conshohocken, PA.
• Taheri-Mandarjani, M., Zarei-Hanzaki, A., & Abedi, H. R. (2015). Hot ductility behavior of an extruded 7075 aluminum alloy. Materials Science and Engineering A, 637,107–122.
• Tekeli, S., Şimşek, İ., Şimşek, D. & Özyürek, D., (2019). Effects of different solid solution temperatures on microstructure and mechanical properties of the AA7075 alloy after T6 heat treatment. High Temperature Materials and Processes, 38 (1), 892-896.
• Viana, F., Pinto, A. M. P., Santos, H. M. C. & Lopes, A. B. (1999). Retrogression and re-ageing of 7075 aluminium alloy: microstructural characterization. Journal of Materials Processing Technology, 92,54–59.
• You, C. P., Thompson, A. W. & Bernstein, I. M. (1995). Ductile fracture processes in 7075 aluminum. Metallurgical And Materials Transactions A, 26 (2), 407–415.
• Zhang, H. B., Wang, B., Zhang, Y. T., Li, Y., He, J. L. & Zhang, Y. F. (2020). Influence of aging treatment on the microstructure and mechanical properties of CNTs/7075 Al composites. Journal of Alloys and Compounds, 814,152357.
• Zhang, P. X., Yan, H., Liu, W., Zou, X. L. & Tang, B. B. (2019). Effect of T6 heat treatment on microstructure and hardness of nanosized Al2O3 reinforced 7075 aluminum matrix composites. Metals, 9 (1),44.
• Zhou, M., Lin, Y. C., Deng, J., & Jiang, Y. Q. (2014). Hot tensile deformation behaviors and constitutive model of an Al-Zn-Mg-Cu alloy. Materials and Design, 59,141–150.
• Zou, X. L., Hong, Y. A. N., & Chen, X. H. (2017). Evolution of second phases and mechanical properties of 7075 Al alloy processed by solution heat treatment. Transactions of Nonferrous Metals Society of China, 27(10), 2146-2155.