حجم آزاد در آهن و مس خالص تغییر شکل پلاستیکی شدید یافته، تشابه ها و تمایز ها

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استاد پژوهشگر، دانشکده مهندسی معدن و متالورژی، دانشگاه صنعتی امیرکبیر، تهران، ایران.

2 استاد، دانشکده مهندسی متالورژی و مواد، پردیس دانشکد ه های فنی دانشگاه تهران، دانشگاه تهران، تهران، ایران.

3 کارشناسی، دانشکده مهندسی متالورژی و مواد، پردیس دانشکد ه های فنی دانشگاه تهران، دانشگاه تهران، تهران، ایران.

4 استاد، بورد تخصصی پزشکی هسته ای، گروه پزشکی هسته‌ ای، مرکز تحقیقات پزشکی هسته ای، دانشگاه علوم پزشکی تهران، تهران، ایران.

چکیده

در پژوهش حاضر، تشکیل حجم آزاد در فلزات آهن و مس خالص فرآوری شده به روش تغییر شکل پلاستیکی شدید با استفاده از نورد شکل دار سرد مورد بررسی قرار گرفت. بدین منظور از میکروسکوپ الکترونی عبوری و میکروسکوپ الکترونی روبشی برای مطالعات ریز ساختاری و از آنالیز های دیلاتومتری و نفوذ رادیو ردیاب و چگالی سنجی جهت بررسی های کمی و کیفی حجم آزاد بهره گرفته شد. نتایج نشان داد کاهش چگالی قابل ملاحظه ای پس از اعمال نورد شکل دار سرد شدید حاصل گردید. نتایج حاصل از بررسی های دیلاتومتری و نفوذ رادیو ردیاب نیز مؤید آن بود که میزان بالایی حجم آزاد در مقایسه با فلزات آنیل شده تشکیل شده است. افزایش نسبی حجم آزاد در نمونه آهن بیش از مس در شرایط مشابه بدست آمد. بررسی های ریزساختاری فلزات فرآوری شده حاکی از تشکیل حجم آزاد به صورت چگالی بالای عیوب جای خالی، نابجایی ها، مرزدانه های غیر تعادلی، اتصالات سه گانه و نانوحفرات می باشد. در واقع، فرآیند نورد شکل دار سرد شدید منجر به ایجاد یک ساختار ناهمگن و فوق ریزدانه همراه با افزایش حجم آزاد در هر دو فلز آهن و مس فرآوری شده در کرنش معادل 5/4 شد، ولی مکانیزم تغییر شکل، نوع ساختار ایجاد شده، اندازه دانه ها، میزان کاهش چگالی و تغییرات حجم آزاد و هم چنین رفتار حرارتی بسته به نوع فلز به دلیل تفاوت در ساختار کریستالی و خواص ذاتی متفاوت بود.

کلیدواژه‌ها


عنوان مقاله [English]

On the free volumes of severely deformed pure Fe and Cu, similarities and differences

نویسندگان [English]

  • Nazanin Forouzanmehr 1
  • Mahmoud Nili-Ahmadabadi 2
  • Hamed Abdous 3
  • Babak Fallahi 4
1 Research Fellow, Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic),Tehran,, Iran.
2 Professor, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran.
3 BSc, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran.
4 Professor, MD, Board of nuclear medicine, Research center for nuclear medicine, Tehran University of Medical Sciences, Tehran, Iran.
چکیده [English]

The present study aims to investigate the formation of free volumes in pure Fe and Cu processed by severe plastic deformation process using cold shape rolling. Transmission electron microscope for microstructural studies as well as dilatometric analyzes, radio tracer technique and density measurement for quantitative and qualitative analysis of free volumes were used. The results showed that a significant decrease in density was achieved after severe cold rolling. The results of dilatometric studies and radio tracer technique also confirmed the formation of high amount of free volumes in the severely deformed metals in comparison with the annealed metals. It was found that the relative increase of free volumes in the severely deformed Fe was higher than that of Cu. It was indicated that the high concentration of free volumes presented in the microstructure of processed metals at vacancies, dislocations, non-equilibrium grain boundaries, triple junctions, and nanovoids. In fact, the severe cold shape rolling process led to the formation of an inhomogeneous and ultrafine microstructure with the increase in free volumes in both processed Fe and Cu metals in the equivalent strain of 4.5. However, deformation mechanisms, microstructure, grain size, density reduction, and free volumes concentration as well as thermal behavior of each metal varied depending on its crystal structure and intrinsic properties.

کلیدواژه‌ها [English]

  • severe plastic deformation
  • Free volumes
  • Nanostructures
  • Non-equilibrium grain boundaries
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