بررسی کارپذیری آلومینیم 7075 پیرسخت شده در فرآیند ایکپ

نوع مقاله : مقاله علمی

نویسندگان
رضا ناصری 1
فرانک دهقانی 2
1 گروه مهندسی مکانیک، دانشگاه ملی مهارت، تهران، ایران
2 گروه مهندسی شیمی، دانشکده مهندسی، دانشگاه گرمسار، گرمسار، ایران
10.22034/stme.2025.538420.1153
چکیده
آلیاژ آلومینیم 7075 به‌عنوان یک فلز پیرسخت‌شونده، علی‌رغم خواص مطلوبی نظیر استحکام ویژه عالی، چقرمگی خوب، شکل‌پذیری نسبتاً مناسب و استحکام خستگی بالا، به دلیل تشکیل فازهای رسوبی پایدار ناشی از پیرسختی، دارای کارپذیری نسبتاً پایینی است. ارتقای کارپذیری این ماده در فرآیند پرس‌کاری در کانال‌های هم‌مقطع زاویه‌دار (ECAP) جهت بهبود خواص مکانیکی، از اهداف این تحقیق است. در این مطالعه، پس از اعمال عملیات پیرسختی طبیعی، کارپذیری این ماده به‌عنوان غلاف در بیلت دو ماده‌ای با هسته از جنس آلومینیم خالص طی فرآیند ایکپ در دمای محیط و زاویه کانال 90 درجه و در دو حالت با و بدون اعمال فشار پشتی مورد ارزیابی قرار گرفت. نتایج نشان داد که در اثر کرنش بالای وارده بعد از یک گذر ایکپ، نشانه‌های زوال در هر دو حالت به وجود آمده است؛ ولی مشاهده شد که علائم زوال ماده‌ی غلاف از وضعیت ترک‌های عمیق، تکه‌تکه‌شدگی و گسیختگی کامل در حالت بدون فشار پشتی به شرایط ترک‌های کم‌عمق و گسست قابل اغماض در حالت با فشار پشتی تقلیل پیدا کرده است. لذا می‌توان دریافت که فشار پشتی در ارتقای کارپذیری این ماده نقش مؤثری ایفا کرده است. نتایج آزمون سختی نیز نشان داد که سختی ویکرز در شرایط آنیل اولیه (103)، پیرسخت شده (129)، ایکپ بدون فشار پشتی (162) و ایکپ با فشار پشتی (178) به ترتیب به میزان 25، 57 و 73 درصد نسبت به حالت آنیل شده اولیه افزایش یافته است که این ارتقای خواص مکانیکی ناشی از اثر هم‌زمان سخت‌کاری رسوبی طی عملیات پیرسازی و اعمال تغییر شکل پلاستیکی شدید با ایکپ سرد می‌باشد.
کلیدواژه‌ها
آلومینیم 7075
پیرسختی طبیعی
ایکپ
فشار پشتی
کارپذیری
موضوعات

عنوان مقاله English

Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process

نویسندگان English

Reza Naseri 1
Faranak Dehghani 2
1 Department of Mechanical Engineering, Technical and Vocational University (TVU), Tehran, Iran
2 Department of Chemical Engineering, Faculty of Engineering, University of Garmsar, Garmsar, Iran
چکیده English

Aluminum alloy 7075, as a Precipitation-hardenable alloys (age-hardening), despite its desirable properties such as excellent specific strength, good fracture toughness, relatively acceptable formability, and high fatigue strength, exhibits relatively low workability due to the formation of stable precipitate phases resulting from precipitation hardening. Enhancing the workability of this material during ECAP process in order to improve its mechanical properties is one of the objectives of this study. In the present investigation, after applying natural aging treatment, the workability of this material as the casing in a bi-material billet with a CP-Al core was evaluated during ECAP at room temperature, with a channel angle of 90°, under two conditions: with and without the application of back pressure. The results indicated that, due to the high imposed strain after one ECAP pass, signs of damage appeared in both conditions; however, it was observed that the damage characteristics of the casing material were reduced from deep cracks, fragmentation, and complete fracture in the condition without back pressure to shallow cracks and negligible separation in the condition with back pressure. Therefore, it can be concluded that back pressure plays an effective role in enhancing the workability of this material. The hardness test results also showed that the Vickers hardness in the initial annealed condition (103), precipitation-hardened condition (129), ECAP without back pressure (162), and ECAP with back pressure (178) increased by 25%, 57%, and 73%, respectively, compared to the initial annealed condition. This improvement in mechanical properties is attributed to the combined effect of precipitation strengthening during the natural aging treatment and the application of severe plastic deformation through cold ECAP.

کلیدواژه‌ها English

Al 7075
Natural age hardening
ECAP
Back pressure
Workability
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