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


عنوان مقاله [English]

Effect of Minor Amount of Scandium on the Microstructure of 7000 Series ‎Aluminium in as Cast, Homogenized and Artificial Age Hardened Conditions

نویسندگان [English]

  • Azam Beigie Kheradmand 1
  • Shamsedin Mirdamadi 2
  • Saeid Nategh 2
1 PhD Student, Department of Materials Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 Professor, ‎Department of Materials Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
چکیده [English]

Two alloys of Al-Zn-Mg-Cu with the same amount of zirconium and different amount ‎of scandium (0.05 and 0.1 wt.%) were melt in the resistance furnace and cast in the cast iron mold ‎and, after doing the tests of ICP, Spectroscopy and DSC, were put under homogenizing, ‎solubility and T6 treatments operations. Using microscopic observations and DSC analysis, the ‎temperature and time of homogenizing the alloys samples were 500°C‏ ‏and 12h and, 490°C and ‎‎12h for Al-Zn-Mg-Cu-0.1Sc-0.09Zr and Al-Zn-Mg-Cu-0.0.05Sc-0.09Zr, respectively. At the ‎dissolution temperature obtained from the results of hardness test and microscopic ‎observations by FESEM, the alloys were subjected to dissolution and then, were put under T6 ‎thermal operations at 120°C for 12 hours. Microscopic investigations showed that the ‎dominant phases in the microstructure of casting were along with T (Al2Mg3Zn3 and copper solid ‎solution and MgZn2 phase, and the eutectic phase formed 10% of the microstructure. Also, ‎investigation of the casting and homogenized microstructure revealed that no phase included ‎scandium and zirconium in the microstructure. After the homogenization ‎operation, the eutectic phase decreased to 3%. The dominant phase observed in the ‎homogeneous microstructure was the phases containing iron. After the dissolution, the volume ‎fraction of the eutectic phase remained constant and the MgZn2 phase. Having performed the ‎T6 thermal operation at 120°C, Al3(Sc,Zr) and MgZn2 nanoparticles were observed at the ‎grain boundary and inside the microstructure.‎ 

کلیدواژه‌ها [English]

  • Al-Zn-Mg-Cu
  • ‎Scandium
  • ‎Zirconium
  • Microstructure
  • ‎Heat treatment

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