بررسی رفتار سیلان و تحولات ریزساختاری سوپرآلیاژ پایه نیکل ریختگیGTD 111 طی آزمون فشار گرم
محورهای موضوعی : فصلنامه علمی - پژوهشی مواد نوین
مهسا محمدپور
1
(دانشجوی کارشناسی ارشد مهندسی متالورژی دانشگاه صنعتی همدان، همدان)
امیر مؤمنی
2
(استادیار و عضو هیأت علمی گروه مهندسی متالورژی دانشگاه صنعتی همدان، همدان)
کلید واژه: فشار گرم, سوپرآلیاژ, GTD-111, انرژی اکتیواسیون,
چکیده مقاله :
به منظور بررسی رفتار تغییرشکل گرم سوپرآلیاژ ریختهگری GTD 111 آزمایشهای فشار گرم در محدوده دمایی °C 1100- 950 و سرعت کرنش های 1-s 1- 001/0 انجام شدند. تمامی منحنیهای سیلان افزایش نسبتاً خطی تنش تا یک نقطه پیک و سپس نزول آن تا کرنش 5/0 را نشان دادند و منطقه تغییرشکل حالت پایدار با تنش ثابت مشاهده نشد. این روند به مهار نابجاییها توسط ساختار دندریتی و تکثیر آنها در نقطه پیک تنش نسبت داده شد. بررسیهای ریزساختاری نشان دادند که کارگرم، باعث شکسته شدن ساختار شبکهای دندریتی و ایجاد سلولهای مجزا میشود. افزایش دمای کارگرم، افزایش تجزیه ساختار و حصول سلولهای بزرگتر در اثر انحلال ذرات شکسته دندریتی را به دنبال داشت. همچنین، با افزایش سرعت تغییر شکل در یک دمای مشخص نرخ تجزیه شبکه دندریتی کاهش و میزان کشیدگی آن در راستای تغییر شکل افزایش یافت. به کمک معادلات بنیادین توانی و نمایی ثوابت ماده n، b و a در نقطه پیک تعیین شدند. همچنین به کمک رابطه بنیادین سینوس هایپربولیک مقدار انرژی فعال سازی تغییر شکل در نقطه پیک و کرنش نمونه 4/0 به ترتیب kJ/mol 947 و kJ/mol 890 تعیین شد. این نتایج نشان دادند که با افزایش کرنش و شکسته شدن ساختار دندریتی به سلولهای مجزا انرژی فعال سازی تغییرشکل کاهش مییابد.
To investigate the behavior of the superalloy deformation behavior of GTD 111 casting, the hot-pressure tests were carried out at a temperature range of 950 -1100 ° C and strain rates of 1- 0.001 s-1. All of the flow curves showed a relatively linear tension increase to one peak point and then its descent to a strain of 0.5, and the region of steady state deformation with constant stress was not observed. This process was attributed to the control of dislocations by the dendritic structure and their amplification at peak point. Microstructural investigations showed that the hot work would break the structure of the dendritic network and create separate cells. An increase in the temperature of the hot work, resulted an increase in the decomposition of the structure and the achievement of larger cells coused by dissolution of broken dendritic particles. Also, with the increase in the rate of deformation at a given temperature, the decomposition rate of the dendritic network decreased and its elongation increased in the direction of the deformation. Using the fundamental constants of material, n, b and a were determined at the peak point. Also, with the help of the fundamental relationship of sinuses hyperbolic, the amount of activation energy at the peak and the strain of 0.4 samples was 947 kJ / mol and 890 kJ / mol, respectively. These results showed that the deformation activation energy decreases with increasing strain and breaking the dendritic structure into distinct cells.
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