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

فصلنامه علمی - پژوهشی مواد نوین

مقاله 7، دوره 8، شماره 30، بهمن 1396، صفحه 73-86   

نوع مقاله: مقاله پژوهشی

نویسندگان

علیرضا دشتی¹؛ محمدحسین شاعری^{* 2}؛ رضا تقی آبادی³

¹دانش آموخته کارشناسی ارشد، بخش مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره) قزوین

²استادیار، بخش مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره) قزوین

³استادیار ، بخش مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره) قزوین

تاریخ دریافت: 04 بهمن 1395،  تاریخ بازنگری: 29 فروردین 1396،  تاریخ پذیرش: 10 اسفند 1396 

چکیده

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.

کلیدواژه‌ها

فرآیندهای ECAP و MDF؛ آلیاژ 7075- Al؛ خواص مکانیکی؛ ریزساختار؛ هدایت الکتریکی

عنوان مقاله [English]

Effects of severe plastic deformation on mechanical properties, electrical conductivity and microstructure of Al-7075 alloy

نویسندگان [English]

A Dashti¹؛ M.H Shaeri²؛ R Taghiabadi³

چکیده [English]

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.

کلیدواژه‌ها [English]

ECAP and MDF processes, Al-7075 alloy, mechanical properties, Microstructure, Electrical Conductivity

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