بررسی اثر روی بر ریزساختار و رفتار انجمادی آلیاژهای Al-Zn-Mg-Cu

نوع مقاله: مقاله پژوهشی

نویسندگان

1 کارشناسی ارشد، دانشکده مهندسی متالورژی و مواد، پردیس دانشکده‌های فنی دانشگاه تهران، دانشگاه تهران،

2 استادیار، دانشکده مهندسی متالورژی و مواد، پردیس دانشکده‌های فنی دانشگاه تهران، دانشگاه تهران،

3 استاد، دانشکده مهندسی متالورژی و مواد، پردیس دانشکده‌های فنی دانشگاه تهران، دانشگاه تهران،

چکیده

در این پژوهش اثر روی بر ریزساختار و رفتار انجمادی آلیاژ فوق مستحکم جدید Al-Zn-Mg-Cu مورد مطالعه قرار گرفت. به منظور مطالعات انجمادی از آنالیز حرارتی منحنی سرمایش استفاده شد. این روش رفتار انجمادی آلیاژ را با دقت مناسب و سرعت بالایی در اختیار قرار می‌دهد. مطالعات ریزساختاری نشان داد که افزایش در میزان روی منجر به افزایش فاصله بازوهای دندریتی، افزایش کسر حجمی فاز‌های ثانویه و ساختار یوتکتیک و تشکیل دندریت‌های خشن و درشت شده است، با این حال افزایش درمیزان روی اثری بر نوع فازهای ثانویه تشکیل شده نداشته است. در مطالعات آنالیز حرارتی، حضور روی منجر به کاهش دمای جوانه زنی شد. به کمک منحنی سرمایش، تشکیل یک فاز در مراحل میانی انجماد مشاهده شد که می‌تواند فاز حاوی آهن Al13Fe4 باشد. دامنه انجمادی در 8 درصد وزنی روی 175 درجه سلسیوس بود که با افزایش روی تا 25 درصد این دامنه به 190 درجه سلسیوس افزایش یافت. با مقایسه نتایج به دست آمده مشاهده شد که افزایش کسر حجمی فازهای ثانویه با افزایش روی در نتایج آنالیز حرارتی و آنالیز تصویری در تطابق بود. همچنین کسر انجماد یافته در نقطه کوهیرنسی دندریتها از 32/0 به 1/0 درصد کاهش یافت که با افزایش در میزان تخلخل از 09/0 به 32/0 در تطابق است.

کلیدواژه‌ها


عنوان مقاله [English]

The effect of zinc on microstructure and solidification characteristics of Al-Zn-Mg-Cu alloys

نویسندگان [English]

  • Saman Mostafapoor 1
  • Mehdi Malekan 2
  • Masoud Emamy 3
1 MSc, Metallurgy and Materials Engineering, School of Metallurgy and Materials Engineering,University of Tehran,
2 Assistant Professor, Metallurgy and Materials Engineering, School of Metallurgy and Materials Engineering,University of Tehran,
3 Professor, Metallurgy and Materials Engineering, School of Metallurgy and Materials Engineering,University of Tehran,
چکیده [English]

In this study, the effect of zinc on microstructure and solidification characteristics of super high strength Al-Zn-Mg-Cu has been investigated. The solidification studies were performed using cooling curve thermal analysis. This method represents quick and accurate results of solidification path of an alloy. The microstructure studies showed increment in the amounts of zinc increases the dendrite arm spacing (DAS), fraction of second phases and eutectic structure and results in a coarse dendrite structure. However, the zinc content did not affect the present phases in this alloying system. Thermal analysis evaluations revealed decrease in nucleation temperature with zinc addition. The formation of Al13Fe4 phase was observed using by cooling curve. The solidification range in the presence of 8wt.% of zinc was 175 °C although the adding of zinc up to 25 wt.% increased it to 190 °C. Cooling curves represented the increase of the fraction of eutectic structure which was in accordance with image analysis results. The addition of zinc resulted in the decrease of the solidified fraction at dendrite coherency point from 0.32 to 0.1 which matched by increment in porosity fraction from 0.09 to 0.32.

کلیدواژه‌ها [English]

  • Al-Zn-Mg-Cu alloy
  • Solidification
  • Thermal Analysis
  • Cooling curve
  • Microstructure
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