اثر مقادیر جزئی اسکاندیم بر ریزساختار آلیاژ آلومینیم سری 7000 در شرایط ریختگی، ‏همگن‌سازی شده و پیرسختی شده مصنوعی

نوع مقاله : مقاله کامل علمی پژوهشی

نویسندگان

1 دانشجوی دکتری، گروه مهندسی مواد، دانشگاه آزاد اسلامی واحد علوم و تحقیقات، تهران، ایران

2 استاد، گروه مهندسی مواد، دانشگاه آزاد اسلامی واحد علوم و تحقیقات، تهران، ایران

10.22034/frj.2019.165921.1069

چکیده

دو آلیاژ ‏Al-Zn-Mg-Cu‏ با مقدار زیرکونیم مساوی و اسکاندیم متفاوت (05/0 و 1/0 درصدوزنی) تحت عملیات ذوب ‏در کوره مقاومتی و ریخته‌گری در قالب چدنی قرار گرفته و پس از انجام آزمایش‌های ‏ICP، کوانتومتری و ‏DSC، ‏تحت عملیات همگن‌کردن، انحلال و عملیات حرارتی ‏T6‎‏ قرار گرفتند. با استفاده از مشاهدات میکروسکپی و آنالیز ‏DSC، دما و زمان همگن‌کردن نمونه‌های آلیاژ به ترتیب ‏°C‏500 و 12 ساعت برای آلیاژ ‏Al-Zn—Mg-Cu-0.1Sc-‎‎0.09Zr‎‏ و ‏‏°C‏490 و 12 ساعت برای آلیاژ ‏Al-Zn-Mg-Cu-0.0.05Sc-0.09Zr‎‏ به دست آمد. آلیاژها در دمای انحلال ‏حاصل از نتایج آزمایش سختی و مشاهدات میکروسکپی توسط ‏FESEM‏ تحت عملیات انحلال قرار گرفته و سپس ‏در دمای ‏C‏‏‏°120 به مدت 12 ساعت تحت عملیات حرارتی ‏T6‎‏ قرار گرفتند. بررسی‌های میکروسکپی نشان داد که ‏فازهای غالب در ریزساختار ریختگی ‏T(Al2Mg3Zn3)‎‏ همراه با محلول جامد مس و فاز ‏MgZn2‎‏ است و فاز ‏یوتکتیک 10 درصد ریزساختار را تشکیل می‌دهد. بررسی ریزساختار ریختگی و همگن شده نشان داد که هیچ فاز حاوی ‏اسکاندیم و زیرکونیمی در ریزساختار وجود ندارد. پس از انجام عملیات همگن‌کردن مقدار فاز یوتکتیک به 3 درصد ‏کاهش یافت. فاز غالب مشاهده شده در ریزساختار همگن‌شده، فازهای حاوی آهن است. پس از عملیات انحلال، ‏کسر حجمی فاز یوتکتیک ثابت مانده و فاز ‏MgZn2‎‏ در زمینه حل شد. پس از انجام عملیات حرارتی ‏T6‎‏ در دمای ‏°C‏120، نانو ذرات‏Al3(Sc,Zr) ‎‏ و ‏MgZn2‎‏ در مرزهای دانه‌ای و درون ریزساختار مشاهده شد.‏

کلیدواژه‌ها

موضوعات


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