بررسی رابطه سختی هال ـ پچ در ناحیه همزده جوش‌های همزن اصطکاکی فولاد کربنی و فولاد زنگ‌نزن آستنیتی

نوع مقاله: مقاله پژوهشی

نویسنده

گروه مهندسی مواد، دانشکده فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

چکیده

جوشکاری همزن اصطکاکی، روشی نوین و موثر برای جوشکاری بسیاری آلیاژهای دارای مشکل جوشکاری و همچنین برای اتصال آلیاژهای غیر همجنس می باشد. در تحقیق حاضر، جوشکاری همزن اصطکاکی برای اتصال غیرهمجنس لب به لب فولاد کم کربن st37 به فولاد زنگ نزن آستنیتی 304 در سرعت های چرخشی مختلف استفاده شده است. نتایج بررسی های آزمایشگاهی نشان داد که ناحیه همزده در فولاد 304 شواهد وقوع بازبلوری پویا را به همراه چگالی متوسطی از نابجایی ها را در خود دارد. ناحیه همزده در فولاد st37 اگرچه در معرض بازبلوری قرار گرفته ولی وقوع استحاله آلوتروپی در حین سرد شدن فولاد پس از جوشکاری، شواهد وقوع بازبلوری را از بین می برد و ریزساختاری حاوی عمدتاً فریت و پرلیت ریز باقی می گذارد. رابطه سختی و ریزساختار از طریق رابطه هال-پچ سختی برای نواحی همزده در هر دو فولاد بررسی گردید. نتایج برازش به روش حداقل مربعات وزنی نشان داد که سختی متوسط نواحی همزده هر دو فولاد طبق رابطه هال-پچ با اندازه دانه، رابطه معکوس دارد. سختی نواحی همزده و فلز پایه فولاد 304 روی یک خط هال-پچ قرار نمی گیرد که این موضوع را می توان به وجود نابجایی های نسبتاً بیشتر ناشی از بازبلوری پویا در نواحی همزده مربوط دانست.

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of hardness Hall-Petch relationship in the stir zone of fiction stir welds between austenitic stainless steel and plain carbon steel

نویسنده [English]

  • Mostafa Jafarzadegan
Materials Science Department, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

Friction stir welding is a new and effective method for joining the alloys with welding problems and also for the dissimilar alloys. In the present study, friction stir welding is used to join st37 low carbon to 304 stainless steel plates at different tool rotation speeds. The stir zone in the 304 steel shows evidence of dynamic recrystallization with a moderate dislocation density. The stir zone in the st37 steel appears to experience dynamic recrystallization too, although the allotropic transformation during cooling cycle of the welds removes the features of dynamic recrystallization and produces a fine ferrite-pearlite microstructure with a low dislocation density. The relationship between hardness and microstructure is investigated through Hall-Petch equation for the stir zone of both steels. The results of weighted least-squares fit also show that the average hardness of austenite in the 304 steel and ferrite in the st37 steel inside the stir zones has a reverse relation with hardness according to the Hall-Petch equation. The hardness of the base metal and the stir zones of 304 steel does not stand on a same Hall-Petch line that can be attributed to the relatively higher dislocations due to the dynamic recrystallization of stir zones.

کلیدواژه‌ها [English]

  • Dissimilar Friction Stir Welding
  • Microstructure
  • Hardness
  • Hall-Petch Relationship

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