ارزیابی خواص مکانیکی تیتانیم خالص فوق ریزدانه تولیدشده توسط فرآیند ایکپ گرم با به‌کارگیری هم‌زمان غلاف و فشار پشتی

نوع مقاله : مقاله علمی

نویسنده
رضا ناصری
استادیار، گروه مهندسی مکانیک، دانشگاه ملی مهارت، تهران، ایران
10.22034/stme.2025.530050.1136
چکیده
به‌کارگیری فرآیند پرس‌کاری در کانال‌های هم‌مقطع زاویه‌دار موسوم به ایکپ (ECAP)، منجر به اعمال کرنش‌های شدید بر ماده‌ی فلزی بیلت می‌شود. در اثر وارد شدن این کرنش‌ها، دانه‌ها از حالت درشت‌دانه‌ی اولیه به فوق‌ریز دانه یا نانوساختار استحاله شده و تحولات میکرو ساختاری مفید در بافت ماده اتفاق می‌افتد که این دگرگونی‌ها به بهبود خواص مکانیکی می‌انجامد. در این تحقیق تیتانیوم خالص BT1-0 به‌عنوان یک ماده سخت کارپذیر در یک غلاف از جنس مس خالص قرارگرفته و تحت چهار گذر فرآیند ایکپ گرم با دمای ºC 250 در کانال 135 درجه و مسیر Bc همراه با اعمال فشار پشتی توسط اکستروژن انتهایی قالب قرار گرفت و اثر هم‌زمان فشار پشتی و غلاف بر ساختار دانه‌بندی و خواص مکانیکی ماده‌ی هدف یعنی تیتانیم خالص بررسی شد. نتایج تجربی نشان داد که دانه‌ها از µm 49 در حالت آنیل شده‌ی اولیه به nm 710 فوق ریزدانه پس از چهار گذر ایکپ تبدیل شدند. استحکام تسلیم فشاری، استحکام نهایی فشاری و تغییر طول نسبی فشاری از MPa 267، MPa 899 و mm/mm 8/51 برای حالت ایکپ نشده به MPa 958، MPa 1375 و mm/mm 7/30 برای حالت چهار گذر ایکپ شده تغییریافته و به ترتیب به میزان 359% افزایش، 153% افزایش و 59% کاهش یافتند. مقدار سختی ویکرز میانگین هم با افزایش از Hv 163 برای حالت آنیل شده‌ی اولیه به Hv 289 بعد از اعمال چهار گذر ایکپ، به میزان 77% ارتقا یافته است.
کلیدواژه‌ها
تیتانیم خالص
فرایند ایکپ گرم
غلاف
فشار پشتی
خواص مکانیکی
موضوعات

عنوان مقاله English

Evaluation of mechanical properties of ultrafine-grained pure titanium produced via warm ECAP process by concurrently utilizing casing and back pressure

نویسنده English

Reza Naseri
1.Assistant Professor, Department of Mechanical Engineering, Technical and Vocational University (TVU), Tehran, Iran
چکیده English

The application of the Equal Channel Angular Pressing (ECAP) process imposes severe plastic strains on the metallic billet. As a result of these imposed strains, the initially coarse grains are transformed into ultra-fined or nanostructured grains, and beneficial microstructural evolutions occur in the texture of the material, which lead to improvements in mechanical properties. In this study, commercially pure titanium (CP-Ti) BT1-0, as a hard-to-deform material, was placed inside a casing made of pure copper and subjected to four passes of warm ECAP at a temperature of 250°C in a 135° channel using route Bc, accompanied by the application of back pressure through extrusion in the end of die. The simultaneous effect of back pressure and the casing on the grain structure and mechanical properties of the target material, i.e., CP-Ti, was evaluated. Experimental results showed that the grain size was refined from 49 µm in the initial annealed state to 710 nm after four ECAP passes. The compressive yield and ultimate strength, and also compressive elongation changed from 267 MPa, 899 MPa, and 51.8 mm/mm in the non-ECAPed condition to 958 MPa, 1375 MPa, and 30.7 mm/mm after ECAP processes, corresponding to increases of 359% and 153%, and a decrease of 59%, respectively. The average Vickers hardness also increased from 163 Hv in the initial annealed state to 289 Hv after four ECAP passes, representing a 77% enhancement.

کلیدواژه‌ها English

Pure titanium
Warm ECAP process
Casing
Back pressure
Mechanical properties

اصل مقاله

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