مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

بکارگیری فرآیند فورج چند جهته برای تولید تیتانیم خالص با ساختار فوق ریزدانه

نویسندگان
ایمان انصاریان 1
محمدحسین شاعری 1
محمود ابراهیمی 2
1 دانشکده مهندسی مواد، دانشگاه بین المللی امام خمینی (ره)، قزوین
2 دانشکده مکانیک دانشگاه مراغه، مراغه
چکیده
تیتانیم خالص تجاری (CP) بدلیل زیست‌سازگاری عالی، کاربرد‌های زیادی در بایومواد و نیز ایمپلنت‌ها دارد. مهم‌ترین نقطه ضعف تیتانیم خالص تجاری استحکام پایین‌ آن در مقایسه با دیگر آلیاژهای تیتانیم می‌باشد. یکی از روش‌هایی که به‌وسیله آن می‌توان استحکام تیتانیم را به مقدار قابل توجهی افزایش داد روش‌های تغییر شکل پلاستیک شدید از قبیل فرآیند‌ فورج چند‌گانه (MDF) می‌باشند. لذا هدف پژوهش حاضر، بهبود استحکام تیتانیم CP از طریق ریزدانه‌سازی آن به‌وسیله فرآیند‌MDF است. بدین منظور قطعات تیتانیم CP پس از 1 ساعت فرآیند آنیل در دمای 800°C، تا 6 پاس تحت فرآیند MDF در دمای محیط قرار گرفتند. بررسی‌های ریزساختاری بوسیله میکروسکوپ نوری و میکروسکوپ الکترونی روبشی مجهز به EBSD انجام گرفت. خواص مکانیکی نیز توسط آزمون‌های میکروسختی و کشش مطالعه شد. همچنین شبیه-سازی اجزای محدود با استفاده از نرم افزار آباکوس جهت پیش‌بینی توزیع کرنش فرآیند MDF انجام گرفت. نتایج بررسی‌ ریزساختار نشان داد که میانگین اندازه دانه پس از اعمال فرآیند MDF کاهش قابل توجهی می‌یابد و افزایش پاس‌های MDF باعث افزایش ریزدانه‌سازی حین فرآیند MDF می‌گردد. پس از 6 پاس فرآیند MDF میانگین اندازه دانه از 45 میکرون به 390 نانومتر کاهش می‌یابد. نتایج خواص مکانیکی نشان داد که استحکام و سختی نمونه‌ها با انجام فرآیند MDF و افزایش تعداد پاس‌های آن افزایش می‌یابند. سختی و استحکام تیتانیم CP پس از 6 پاس MDF حدود 2 برابر مقادیر متناظر آنها در نمونه آنیل شده بدست می‌آید. همچنین نتایج توزیع کرنش حاصل از شبیه‌سازی و توزیع میکروسختی نمونه‌های MDF شده نیز مطابقت خوبی نشان می‌دهند.
کلیدواژه‌ها
فورج چند جهته
تیتانیم خالص تجاری
آنالیز المان محدود
خواص مکانیکی
بررسی ریزساختاری

عنوان مقاله English

Utilization of multi directional forging for fabrication of ultrafine-grained pure titanium

نویسندگان English

iman ansarian 1
mohammad hossein shaeri 1
Mahmoud Ebrahimi 2
1 Materials Science and Engineering Department, Imam Khomeini International University (IKIU), Qazvin, Iran
2 Department of Mechanical Engineering, University of Maragheh, Maragheh, Iran.
چکیده English

Commercial pure (CP) titanium has many applications in biomaterials especially in implants due to its excellent biocompatibility. The major weakness of CP titanium is low strength compared to that of other titanium alloys. One of the methods can be used to increase the strength of CP titanium are severe plastic deformation methods such as multi directional forging (MDF). Therefore, the aim of this research is the improvement of CP titanium strength by grain refinement in MDF process. For this purpose, after one hour annealing at 800°C, the CP titanium was forged by MDF process up to six passes at ambient temperature. Microstructural studies were performed by optical microscope and scanning electron microscope equipped with EBSD. Mechanical properties were also studied by Vickers’ microhardness and tensile tests. The finite element simulation by Abaqus software was also applied to predict the strain distribution during MDF process. The results of microstructural analysis showed that the average grain size decreased significantly after the MDF process and increasing the pass numbers of MDF led to an increase in grain refinement. After six passes of the MDF process, the average grain size decreased from 45 microns to 390 nm. Mechanical properties results showed that the strength and hardness of specimens increased with MDF process and increasing the number of passes. The hardness and strength of six passes MDFed specimen was about 2 times greater than those of annealed specimen. The strain distribution results obtained from the simulation showed good agreement with experimental results of microhardness distribution.

کلیدواژه‌ها English

Multi directional forging
Commercial pure titanium
Finite element analysis
Mechanical properties
Microstructure study
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مهندسی مکانیک مدرس
دوره 18، شماره 2
اردیبهشت 1397
صفحه 371-382