بررسی اثر تغییر شکل پلاستیک شدید بر ریزساختار، خواص مکانیکی و هدایت الکتریکی آلیاژ آلومینیوم 7075

محورهای موضوعی : فصلنامه علمی - پژوهشی مواد نوین

علیرضا دشتی ¹ (دانش آموخته کارشناسی ارشد، بخش مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره) قزوین)
محمدحسین شاعری ² (استادیار، بخش مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره) قزوین)
رضا تقی آبادی ³ (استادیار ، بخش مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره) قزوین)

تاریخ دریافت : 1395/11/04 تاریخ پذیرش : 1396/12/10 تاریخ انتشار : 1396/12/01

کلید واژه: هدایت الکتریکی, ریزساختار, خواص مکانیکی, فرآیندهای ECAP و MDF, آلیاژ 7075- Al,

چکیده مقاله :

هدف پژوهش حاضر، بررسی خواص مکانیکی، هدایت الکتریکی و ریزساختار آلیاژ آلومینیوم 7075 پرس شده به­وسیله فرآیندهای پرس در کانال­های همسان زاویه­دار (ECAP) و فورج چندجهتی (MDF) می­باشد. در این پژوهش آلیاژ 7075 در حالت عملیات حرارتی آنیل تحت 4 پاس فرآیند ECAP و 3 پاس فرآیند MDF در دمای محیط قرار گرفت. خواص مکانیکی نمونه­ها با استفاده از آزمون­های سختی و پانچ برشی و ریزساختار نمونه­ها با استفاده از میکروسکوپ الکترونی عبوری (TEM) بررسی شد. در ضمن هدایت الکتریکی نمونه­ها نیز به روش جریان گردابی اندازه­گیری شد. نتایج این پژوهش نشان می­دهد، 4 پاس فرآیند ECAP، باعث افزایش قابل ملاحظه خواص مکانیکی (حدود 2 برابر) و ریزدانه شدن تا اندازه­ دانه کم­تر از 400 نانومتر می­شود؛ در ضمن اکثر دانه­ها پس از ECAP هم­محور بوده و بخش عمده مرزهای دانه زاویه ­بزرگ­ می­باشند. از طرف دیگر، تاثیر فرآیند MDF بر ریزدانه­سازی و افزایش خواص مکانیکی کم­تر از فرآیند ECAP بوده به طوری­که پس از 3 پاس MDF خواص مکانیکی حدود 50 درصد افزایش یافته و اندازه دانه نمونه­ها به کم­تر از 1000 نانومتر کاهش یافته است. در ضمن در فرآیند MDF کسر مرزهای بزرگ زاویه کم­تر از فرآیند ECAP می­باشد. نتایج بررسی هدایت الکتریکی نشان داد، حین فرآیندهای ECAP و MDF، هدایت الکتریکی آلیاژ 7075 به مقدار بسیار اندکی کاهش می­یابد. لذا می­توان عنوان نمود، ریزدانه سازی به­وسیله فرآیندهای ECAP و MDF یکی از روش­هایی است که می­توان به­وسیله آن استحکام را بدون کاهش قابل ملاحظه هدایت الکتریکی افزایش داد.

چکیده انگلیسی:

The aim of current research was to examine the microstructure, mechanical properties and electrical conductivity of Al-7075 alloy that develops during Equal Channel Angular Pressing (ECAP) and Multi Directional Forging (MDF). The Annealed Al-7075 alloy was subjected up to 3 and 4 passes of MDF and ECAP deformation at room temperature, respectively. Followed by ECAP, Vickers microhardness and shear punch test were performed and microstructural observations were undertaken using transmission electron microscopy (TEM). The electrical conductivity was also measured by eddy current method. Microstructural investigations show that after 4 passes of ECAP very fine grains with average grain size of about 350 nm appear and most of the grains evolve into arrays of high angle boundaries. On the other hand, 3 passes of MDF leads to higher grain size (950 nm) and lower fraction of high angle boundaries compared with 4 pass of ECAP. Mechanical properties of specimens increase about 100 and 50 percent after 3 passes of MDF and 4 passes of ECAP, respectively. So, it can be concluded that the ECAP process is more effective than the MDF process in grain refinement and improvement of mechanical properties. The electrical conductivity measurement at room temperature showed that there was no significant change in the conductivity of the processed samples compared with the initial specimen. Finally, it can be deduced that grain refinement during ECAP and MDF processes can be considered as a strategy to improve mechanical strength of pure metals without sacrifice of their electrical conductivity.

منابع و مأخذ:

1- R.Z. Valiev, T.G. Langdon, “Principles of Equal-Channel Angular Pressing as a Processing Tool for Grain Refinement”, Progress in Materials Science, Vol. 51, pp. 881-981, 2006.

2- ز. عباسی و ر. ابراهیمی، ”مطالعه تبلورمجدد استاتیکی مس پس از تغییرشکل پلاستیک شدید“، نشریه مواد نوین، جلد 5 شماره 2، ص 109-116، زمستان 1393.

3- R.Z. Valiev, R.K. Islamgaliev, I.V. Alexandrov, “Bulk nanostructured materials from severe plastic deformation”, Progress in Materials Science, Vol. 45, pp. 103-189, 2002.

4- A. Vinogradov, V. Patlan, Y. Suzuki, K. Kitagawa, V.I. Kopylov, “Structure and properties of ultra-fine grain Cu–Cr–Zr alloy produced by equal-channel angular pressing”, Acta Materialia, Vol. 50, pp. 1639-1651, 2002.

5- E. Cerri, P. Leo, “Influence of severe plastic deformation on aging of Al–Mg–Si alloys”, Materials Science and Engineering A, Vol. 410-411, pp. 226-229, 2005.

6- Y.G. Ko, S.N. Byung, U. Lee, D.H. Shin, “Mechanical and electrical responses of nanostructured Cu–3 wt%Ag alloy fabricated by ECAP and cold rolling”, Journal of Alloys and Compounds, Vol. 504, pp.448-451, 2010.

7- C. Xu,, T.G. Langdon, “Influence of a round corner die on flow homogeneity in ECA pressing”, Scripta Materialia, Vol. 48, pp. 1-4, 2003.

8- C. Xu, T.G. Langdon, “The development of hardness homogeneity in aluminum and an aluminum alloy processed by ECAP”, Journal of Materials Science, Vol. 42, pp. 1542-1550, 2007.

9-P.N. Rao, D. Singh, R. Jayaganthan. “Mechanical Properties and Microstructural Evolution of Al 6061 alloy processed by Multi Directional Forging at Liquid nitrogen temperature”, Materials and Design, Vol. 56, pp. 97-104, 2014.

10- O. Sitdikov, T. Sakai, A. Goloborodko, H. Miura, R. Kaibyshev, “Effect of Pass Strain on Grain Refinement in 7475 Al Alloy during Hot Multidirectional Forging”, Materials Transactions, Vol. 45, pp. 2232-2238, 2004.

11- س. خانی مقانکی و م. کاظمی­نژاد، ”تاثیر تغییر شکل پلاستیک شدید روی رفتار پیری طبیعی آلیاژ آلومینیوم 2024“، نشریه مواد نوین، جلد 6 شماره 3، ص 39-46، بهار 1395.

12- K. Stiller, P.J. Warren, V. Hansen, J. Angenete, J. Gjonnes, “Investigation of precipitation in an Al–Zn–Mg alloy after two-step ageing treatment at 100° and 150°C”, Materials Science & Engineering A, Vol. 270, pp. 55-63, 1999.

13- K.S. Ghosh, N. Gao, M.J. Starink, “Characterisation of high pressure torsion processed 7150 Al-Zn-Mg-Cu alloy”, Materials Science & Engineering A, Vol. 552, pp. 164-171, 2012.

14- F. Akbaripanah, F. Fereshteh-Saniee, R. Mahmudi, H.K. Kim, “Microstructural homogeneity, texture, tensile and shear behavior of AM60 magnesium alloy produced by extrusion and equal channel angular pressing”, Materials and Design Vol. 43, pp. 31-39, 2013.

15- M.H. Shaeri, M. Shaeri, M.T. Salehi, S.H. Seyyedein, F. Djavanroodi, “Microstructure and texture evolution of Al-7075 alloy processed by equal channel angular pressing”, Transaction Nonferrous Metal Society of China, Vol. 25, pp. 1367-1375, 2015.

16- M. Vaseghi, A. Karimi Taheri, S.I. Hong, H.S. Kim, “Dynamic ageing and the mechanical response of Al-Mg-Si alloy through equal channel angular pressing”, Materials and Design, Vol. 31, pp. 4076-4082, 2010.

17- P.W.J. Mckenzie, R. Lapovok, Y. Estrin, “The influence of back pressure on ECAP processed AA 6016: Modeling and experiment”, Acta Materialia, Vol. 55, pp. 2985-2993, 2007.

18- C.M. Cepeda-Jiménez, J.M. García-Infanta, O.A. Ruano, F. Carreño, “High strain rate superplasticity at intermediate temperatures of the Al 7075 alloy severely processed by equal channel angular pressing”, Journal of Alloys and Compounds, Vol. 509, pp. 9589-9597, 2011.

19- K. Nakashima, Z. Horita, M. Nemoto, T.G. Langdon, “Influence of channel angle on the development of ultrafine grains in equal-channel angular pressing”, Acta Materialia, Vol. 46, pp. 1589-1599, 1998.

20- M.H. Shaeri, M.T. Salehi, S.H. Seyyedein, M.R. Abutalebi, J.K. Park, “Microstructure and mechanical properties of Al-7075 alloy processed by equal channel angular pressing combined with aging treatment”, Materials and Design, Vol. 57, pp. 250-257, 2014.

21- B. Tolaminejad, K. Dehghani, “Microstructural characterization and mechanical properties of nanostructured AA1070 aluminum after equal channel angular extrusion”, Materials and Design, Vol. 34, pp. 285–292, 2012.

22- M. Reihanian, R. Ebrahimi, M.M. Moshksar, D. Terada, N. Tsuji, “Microstructure quantification and correlation with flow stress of ultrafine grained commercially pure Al fabricated by equal channel angular pressing (ECAP) ”, Materials Characterization, Vol. 59, pp. 1312–1323, 2008.

23- W.Q. Cao, A. Godfrey, Q. Liu, “EBSP investigation of microstructure and texture evolution during equal channel angular pressing of aluminium”, Materials Science and Engineering A, Vol. 361, pp. 9–14, 2003.

24- W. Skrotzki, N. Scheerbaum, C.G. Oertel, R. Arruffat-Massion, S. Suwas, L.S. Toth, “Microstructure and texture gradient in copper deformed by equal channel angular pressing”, Acta Materialia, Vol. 55, pp. 2013–2024, 2007.

25- M.H. Shaeri, M. Shaeri, M. Ebrahimi, M.T. Salehi, S. H Seyyedein, “Effect of ECAP temperature on microstructure and mechanical properties of Al–Zn–Mg–Cu alloy”, Progress in Natural Science: Materials International, Vol. 26, pp. 182-191, 2016.

26- J. Kavosi, M. Saei, M. Kazeminezhad, A. Dodangeh, “Modeling of dislocation density and strength on rheoforged A356 alloy during multi-directional forging”, Computational Materials Science, Vol. 81, pp. 284-289, 2014.

27- J. Gubicza, I. Schiller, N.Q. Chinh, J. Illy, Z. Horita, T.G. Langdon, “The effect of severe plastic deformation on precipitation in supersaturated Al–Zn–Mg alloys”, Materials Science & Engineering A, Vol. 460-461, pp. 77-85, 2007.

28- S. Dadbakhsh, A. Karimi Taheri, C.W. Smith, “Strengthening study on 6082 Al alloy after combination of aging treatment and ECAP process”, Materials Science & Engineering A, Vol. 527, pp. 4758–4766, 2010.

29- N.Q. Chinh, J. Gubicza, T.G. Langdon “Characteristics of face-centered cubic metals processed by equal-channel angular pressing”, Journal of Materials Science, Vol. 42, pp. 1594-1605, 2007.

30- Y.H. Zhao, X.Z. Liao, Z. Jin, R.Z. Valiev, Y.T. Zhu, “Microstructures and mechanical properties of ultrafine grained 7075 Al alloy processed by ECAP and their evolutions during annealing”, Acta Materialia, Vol. 52, pp. 4589-4599, 2004.

31- Z. Horita, T. Fujinami, M. Nemoto, T.G. Langdon, “Equal-channel angular pressing of commercial aluminum alloys: grain refinement, thermal stability and tensile properties”, Metallurgical and Materials Transaction A, Vol. 31, pp. 691-791, 2000.

32- W. Yan, X. Liu, J. Huang, L. Chen, “Strength and ductility in ultrafine-grained wrought aluminum alloys”, Materials and Design, Vol. 49, pp. 520-524, 2013.

33- K. Venkateswarlu, M. Ghosh, A. Ray, C. Xu, T.G. Langdon, “On the feasibility of using a continuous processing technique incorporating a limited strain imposed by ECAP”, Materials Science & Engineering A, Vol. 485, pp. 476-480, 2008.

34- C.S. Pande, K.P. Cooper, “Nanomechanics of Hall–Petch relationship in nanocrystalline materials”, Progress in Material Science, Vol. 54, pp. 689-706, 2009.

35- M. Furukawa, Z. Horita, M. Nemoto, R.Z. Valiev, T.G. Langdon, “Microhardness measurments and the Hall-Petch relationship in an Al-Mg alloy with submicrometer grain size”, Acta Materialla, Vol. 44, pp. 4619-4629, 1996.

36- M. Furukawa, Z. Horita, M. Nemoto, R.Z. Valiev, T.G. Langdon, “Factors influencing the flow and hardness of materials with ultrafine grain sizes”, Philosophical Magazine A, Vol. 78, pp. 203-215, 1998.

37- M.Y. Murashkin, I. Sabirov, X. Sauvage, R.Z. Valiev, “Nanostructured Al and Cu alloys with superior strength and electrical conductivity”, Journal of Materials Science, Vol. 51, pp. 33-49, 2016.

38-M.Y. Murashkin, I. Sabirov, V.U. Kazykhanov, E.V. Bobruk, A.A. Dubravina, R.Z. Valiev, “Enhanced mechanical properties and electrical conductivity in ultrafine-grained Al alloy processed via ECAP-PC”, Journal of Materials Science, Vol. 48, pp. 4501-4509, 2013.

39- A. Afsari, M.A. Ranaei, “Equal Channel Angular Pressing to Produce Ultrafine Pure Copper with Excellent Electrical and Mechanical Properties”, International Journal of Nanoscience and Nanotechnology, Vol. 10, pp. 215-222, 2014.