بررسی شکل‌پذیری تیتانیم خالص تجاری در فرآیند پرسکاری در کانال‌های زاویه‌دار با مقاطع همسان

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار، مهندسی مواد، دانشگاه صنعتی ارومیه، ارومیه، ایران

2 استاد، مهندسی مواد، دانشگاه صنعتی سهند، تبریز، ایران

چکیده

ریز کردن اندازه دانه تا محدوده زیر میکرون با استفاده از روش‌های تغییر شکل پلاستیک شدید از مؤثرترین مکانیزم‌های استحکام دهی فلزات و آلیاژها محسوب می‌شود. با این حال فلزات با قابلیت شکل‌پذیری پایین مانند تیتانیم در جریان اعمال تغییر شکل دچار ترک خوردگی و شکست می‌شوند. لذا تلاش‌ها برای تحمیل کرنش پلاستیک سنگین به آنها که از ملزومات ریز شدن اندازه دانه است عموماً موفقیت آمیز نیست. در تحقیق حاضر تیتانیم خالص تجاری تحت فرآیند پرسکاری در کانال‌های زاویه‌دار با مقاطع همسان قرار گرفت. به منظور بهبود شکل‌پذیری، زاویه کانال قالب بازتر از مقدار رایج ◦90 یعنی ◦105 در نظر گرفته شد و اثردما (300، 250، 200 درجه سانتی‌گراد)، سرعت پرس (10، 1، 1/0 و 01/0 میلی‌متر بر ثانیه ) و ریز ساختار اولیه بر شکل‌پذیری تیتانیم بررسی شد. نتایج حاکی از آن است که با کاهش سرعت پرس، شکل‌پذیری تیتانیم بهبود می‌یابد. همچنین استفاده از زاویه کانال بزرگتر امکان کاهش دمای فراوری را به اندازه ◦C150 نسبت به تحقیقات انجام شده قبلی فراهم می‌آورد به گونه‌ای که میله‌های تیتانیم در این تحقیق در دمای ◦C250 تا 10 پاس بصورت سالم و بدون ترک خوردگی فراوری شدند. علاوه بر آن، دیده شد که ریز ساختار اولیه هم محور نسبت به ریز ساختار لایه‌ای شکل‌پذیری بسیار بهتری از خود نشان می‌دهد. مشاهدات با میکروسکوپ نوری از ریز ساختار میله‌های فراوری شده حاکی از آن است که ترکها از نواحی تمرکز کرنش جوانه زده و رشد پیدا می‌کنند.

کلیدواژه‌ها

عنوان مقاله [English]

Investigation of formability of commercially pure titanium in equal channel angular pressing process

نویسندگان [English]

  • kaveh Hajizadeh 1
  • Beitallah Eghbali 2
1 Department of Materials Engineering, Urmia University of Technology, Urmia, Iran
2 Faculty of Materials Engineering, Sahand University of Technology, Tabriz, Iran
چکیده [English]

Grain size refining down to sub-micrometer range using severe plastic deformation methods is known as an effective strengthening mechanism in metals and alloys. However, metals with low formability such as titanium are subjected to cracking and fracture when they are severely deformed. As a result, attempts to impose intense plastic strain to them which is essential for grain refinement are generally not successful. In the present study commercially pure titanium was severely deformed by equal channel angular pressing. In order to enhance the formability, a larger channel of 105˚ was selected instead of common angle of 90˚and the effect ECAP temperature (300, 250, and 200 ˚C), pressing speed (10, 1, 0.1, 0.01 mm/s), and the initial microstructure on the formability of titanium was investigated. The results indicate that by lowering the pressing speed the formability is improved. Also, the use of a larger channel angle provides the possibility of reducing the processing temperature by 150 ˚C compared to previous researches, such that the titanium bars were processed at a temperature of 250 ˚C safely and without cracking up to 10 passes. Moreover, it was seen that the initial equiaxed microstructure shows much better formability than lamellar one. Light microscopy observations of the microstructure of the processed bars indicate that cracks nucleate and grow from the regions in which the material experienced higher amounts of strain.

کلیدواژه‌ها [English]

  • Commercially pure titanium
  • ECAP
  • Formability
  • Pressing speed
  • Initial microstructure

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مهندسی ساخت و تولید ایران
دوره 9، شماره 7
مهر 1401
صفحه 49-63

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