مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

بررسی رفتار میکرومکانیک فریت و مارتنزیت در فولادهای دوفازی

نویسندگان
گروه مهندسی مواد، دانشکده مهندسی، دانشگاه بوعلی سینا، همدان، ایران
چکیده
هدف از این پژوهش، بررسی رفتار میکرومکانیک فریت و مارتنزیت در فولادهای دوفازی بود. بدین منظور یک فولاد کم‌کربن با ساختار اولیه فریتی- پرلیتی تا۸۰% نورد سرد و آنیل متعاقب در دمای C°۶۰۰ به‌مدت ۲۰دقیقه و کوئنچ در آب شد. مرحله پایانی فرآوری شامل گرمایش تا ناحیه بین‌بحرانی و نگهداری در دماهای ۷۶۰، ۷۸۰، ۸۰۰ و C°۸۲۰ به‌مدت ۱۰دقیقه و کوئنچ در آب بود. فولادهای دوفازی با کسرهای حجمی فریت و مارتنزیت متفاوت و اندازه دانه‌های فریت مختلف تولید شد. تغییرات ریزساختاری و ارتباط آنها با تغییرات سختی فازها به‌کمک میکروسکوپ الکترونی روبشی مجهز به طیف‌سنج توزیع انرژی و آزمون نانوفرورونده بررسی شد. مطالعه نانوفرورونده پاسخ سختی فریت و مارتنزیت در ریزساختارهای دوفازی نشان داد که با افزایش دمای آنیل بین‌بحرانی از ۷۶۰ به C°۸۲۰ متوسط نانو سختی فریت و مارتنزیت به‌ترتیب از ۱۸۱ به ۲۸۱ویکرز افزایش و از ۶۴۴ به ۳۳۷ویکرز کاهش می‌یابد. دماهای آنیل بین‌بحرانی بالاتر به دانه‌های فریت ریزتر و سخت‌تر در ریزساختارهای دوفازی ‌انجامیده است. تغییرات نانوسختی مارتنزیت با دماهای آنیل بین‌بحرانی به تغییرات محتوای کربن مارتنزیت مرتبط شد. با اعمال قانون مخلوط‌ها، مقادیر سختی محاسبه‌شده تطابق خوبی با مقادیر اندازه‌گیری‌شده داشت.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Investigation of Micromechanical Behavior of Ferrite and Martensite in Dual Phase Steels

نویسندگان English

A.H. Jahanara
Y. Mazaheri
M. Sheikhi
Materials Engineering Department, Engineering Faculty, Bu-Ali Sina University, Hamedan, Iran
چکیده English

The aim of this research was to investigate ferrite and martensite micromechanical behavior in dual phase (DP) steels. For this purpose, a low carbon steel with ferrite-pearlite initial structure was cold-rolled up to 80% and annealed at 600 ºC for 20 min and subsequently water quenched. The final processing step involved heating to the intercritical annealing region and holding for 10 min at 760, 780, 800 and 820 ºC followed by water quenching. DP steels consisting different volume fractions of ferrite and martensite and different ferrite grain size were produced. Scanning electron microscopy was supplemented by energy dispersive spectroscopy (EDS) and nanoindentation test to follow microstructural changes and their correlations to the variation in phase's hardness. Nanoindentation study of ferrite and martensite hardening response in the DP microstructures showed that the average ferrite and martensite nanohardness has significantly increased from about 181 to 281 HV10mN and decreased from about 644 to 337 HV10mN with increasing intercritical annealing temperatures from 760 to 820 ºC, respectively. Higher intercritical annealing temperatures resulted in finer and harder ferrite grains in DP microstructures. Martensite nanohardness variation with intercritical annealing temperatures is related to change in its carbon content. By applying the rule of mixtures, the calculated hardness values meet well with the experimental values.

کلیدواژه‌ها English

dual phase steel
Intercritical annealing
Micromechanical behavior
Nanoindentation
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