ارزیابی حرارت ورودی بر تحولات ریزساختاری و خواص مکانیکی اتصال آلیاژ آلومینیم 7020-T6 در جوشکاری TIG

نوع مقاله : علمی و پژوهشی

نویسندگان

دانشگاه شهید چمران اهواز

چکیده

در این پژوهش از فرایند جوشکاری TIG با جریان پالسی و ثابت برای اتصال آلیاژ آلومینیم 7020-T6 استفاده شد. تأثیر شدّت‌جریان (حرارت ورودی) بر ریزساختار و خواص مکانیکی نمونه‌های جوشکاری شده و همچنین تغییرات پهنای منطقۀ متأثر از حرارت، مورد بررسی قرار گرفت. به‌وسیله کاشتن ترموکوپل در ناحیه اتصال تغییرات دمایی اندازه‌گیری و مورد بررسی قرار گرفت. بررسی‌های ریزساختاری توسط میکروسکوپ نوری و الکترونی روبشی انجام گردید. به‌منظور بررسی دمای تشکیل رسوبات، آنالیز گرما سنجی افتراقی (DSC) انجام گردید. همچنین آزمون میکرو سختی و کشش جهت ارزیابی خواص مکانیکی به عمل آمد. بررسی‌ها نشان داد در جوشکاری TIG پالسی نسبت به TIG معمولی کاهش فراوانی در اندازۀ دانه ناحیۀ جوش صورت گرفته، ولی با افزایش حرارت ورودی اندازۀ دانه این ناحیۀ و پهنای منطقۀ متأثر از حرارت نیز افزایش نسبی یافته است. نتایج نشان داد که بر خلاف نتایج مطالعات پیشین در آلیاژهای رسوب سخت شونده، استحکام در ناحیۀ­ی جوش نسبت به فلز زمینه افزایش قابل‌توجّهی یافته است. بهبود نسبی خواص مکانیکی در ناحیه جوش علیرغم افزایش حرارت ورودی و افزایش نسبی اندازۀ دانه‌ها، به دلیل انیل انحلالی و رسوب مجدد ذرات رسوبی استحکام‌بخش در حین سرد کردن از دمای اتصال ارزیابی گردید.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of heat input on microstructure and mechanical properties of A7020-T6 alloy joined by TIG welding

نویسندگان [English]

  • Mohamad Alipour Behzadi
  • Khalil Ranjbar
  • Reza Dehmolaei
Shahid Chamran University of Ahvaz
چکیده [English]

In this study butt joining of 7020-T6 alloy was performed using tungsten inert gas (TIG) welding with continuous (constant) and pulsed current. Effect of heat input on microstructure and mechanical properties of the joints was investigated. Microstructural examinations were conducted using optical and scanning electron microscopy. Differential scanning calorimetry (DSC) was used to identify the precipitates phase evolution. Temperature at the welding region was recorded by inserting thermocouples. Hardness and tensile strength of the joints was evaluated. Results showed that current pulsing leads to relatively finer grain size in weld metal compare to the one welded by constant current. In either cases of constant and pulsed current, the grain size and the width of heat affected zone increased with increasing heat input. Unlike earlier studies in precipitation hardening aluminum alloys, strength of the weld metal were increased as compare to base metal in T6 condition. The enhancement in mechanical properties of weld metal was attributed to the solution annealing and re-formation of strengthening precipitates on cooling from welding temperature.

کلیدواژه‌ها [English]

  • A7020-T6 alloy
  • TIG Welding
  • Microstructural Evolution
  • Heat Input
  • Heat Affected Zone
  • Mechanical Evolution
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