اثر نورد سرد و آنیل کوتاه مدت روی ریزساختار و سختی آلیاژ آلومینیم A356

نوع مقاله: مقاله پژوهشی

نویسندگان

دانشکده مهندسی مواد، دانشگاه صنعتی نوشیروانی بابل، بابل، ایران

چکیده

در این پژوهش، اثر نورد سرد و عملیات حرارتی کوتاه‌مدت روی ریزساختار و سختی آلیاژ آلومینیم 356A بررسی شد. مشاهدات ریزساختاری توسط میکروسکوپ نوری، آنالیز کمّی با استفاده از نرم‌افزار کلمکس و آزمون سختی‌سنجی توسط سختی‌سنج برینل انجام شد. نتایج نشان داد که فرایند نورد باعث ریز شدن، افزایش کرویت و کاهش نسبت طول به عرض ذرات سیلیسیم و نیز حذف تخلخل‌های موجود در نمونه‌ی ریختگی شد. توزیع ذرات سیلیسیم در مقطع RD-ND نسبت به مقطع RD-TD یکنواخت‌تر بود زیرا در فرایند نورد ورق تغییرات ابعادی فقط در جهات RD و ND رخ می‌دهد و در نتیجه تغییرشکل پلاستیک بیش‌تری در مقطع RD-ND به وجود آمده و توزیع ذرات سیلیسیم که کاملا وابسته به مقدار تغییرشکل پلاستیک است در این مقطع یکنواخت‌تر شد. همچنین، نورد و عملیات حرارتی موجب ریزشدن دانه‌های آلومینیم از طریق فعالسازی مکانیزم‌های تبلورمجدد پیوسته و جوانه‌زنی تحریک شده توسط ذرات شد. ذرات سیلیسیم علاوه بر این که موجب تولید دانه‌های ریزتری شدند، از رشد این دانه‌ها نیز جلوگیری کردند. فرایند نورد موجب افزایش سختی نمونه شد اما انجام عملیت حرارتی تا 300 ثانیه، سختی را کاهش داد. در نهایت، افزایش زمان عملیات حرارتی به 600 ثانیه به دلیل کامل شدن مکانیزم تبلورمجدد پیوسته موجب افزایش سختی به میزان 26% گردید.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of cold rolling and short-term annealing on microstructure and hardness of A356 aluminum alloy

نویسندگان [English]

  • Mohammad Amin Jafari Jozan
  • Roohollah Jamaati
Department of Materials Engineering, Babol Noshirvani University of Technology, Babol, Iran
چکیده [English]

In this research, the effect of cold rolling and short-term heat treatment on the microstructure and hardness of A356 aluminum alloy were investigated. Microstructural observations by optical microscopy, quantitative analysis using Clemex software and hardness test by Brinell macrohardness were performed. The results showed that the rolling process led to refining, increasing the sphericity, and decreasing the aspect ratio of the silicon particles, as well as removal of porosity in the casting sample. The distribution of silicon particles at the RD-ND plane was more uniform than the RD-TD and section because during the rolling process, the dimensional changes occurs only in the RD and ND directions, resulting in more plastic deformation at the RD-ND plane, and the distribution of silicon particles which is totally dependent on the amount of plastic deformation became more uniform. Also, rolling and heat treatment caused the grain refinement of aluminum through activation of continuous recrystallization and particle stimulated nucleation (PSN) mechanisms. The presence of silicon particles resulted in formation of finer grains and also suppression of the grain growth. Rolling process increased the hardness of the sample, but the heat treatment up to 300 s reduced the hardness. Finally, increasing the heat treatment time to 600 s resulted in an increase in hardness of 26% due to the completion of the continuous recrystallization mechanism.

کلیدواژه‌ها [English]

  • Aluminum alloy
  • Rolling
  • Annealing
  • Microstructure
  • Hardness

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