بررسی ریزساختار و خواص مکانیکی آلیاژ A356 پس از فرآیند پرسکاری در کانال های هم مقطع زاویه دار و شبیه سازی آن

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد / گروه مکانیک، دانشکده مهندسی، دانشگاه آزاد اسلامی واحد کرمان

2 عضو هیات علمی / گروه مکانیک، دانشکده مهندسی، دانشگاه آزاد اسلامی واحد شیراز

چکیده

پرسکاری در کانال­های هم مقطع زاویه‌دار، یکی از مهم­ترین روش­های تغییر شکل پلاستیک شدید برای ایجاد موادی با دانه‌های فوق‌العاده ریز در فلزات و آلیاژها می­باشد که کاربرد وسیعی در صنایع هوا فضا دارد. هدف از این تحقیق، مطالعه بهبود و اصلاح ریزساختار و خواص مکانیکی آلیاژ آلومینیوم (A356) توسط پرسکاری در کانال­های هم مقطع زاویه‌دار است. برای این منظور، قالبی با زاویه برخورد کانال 120 و زاویه انحنای خارجی 20 درجه طراحی و ساخته شد. فرآیند پرسکاری در دمای محیط انجام گردید، علاوه بر این نمونه­ها پیش از انجام عملیات، آنیل شده و تحت عملیات محلول سازی قرار گرفتند. آزمون‌های سختی، فشار و کشش بعد از انجام فرآیند روی نمونه‌ها انجام شد و ریز ساختار نمونه­ها قبل و پس از پرسکاری، با میکروسکوپ نوری ارزیابی گردید. خواص مکانیکی نمونه‌ها مورد بررسی قرار گرفت و سطح مقطع شکست آنها توسط میکروسکوپ الکترونی روبشی (SEM) ارزیابی شد. نتایج حاصل نشان داد که میزان سختی در نمونه آنیل شده با دو مرحله عبور از 48 به 84/2 ویکرز و میزان استحکام کششی نهایی با یک مرحله عبور از 57 به 177 مگاپاسکال افزایش یافت. شبیه سازی فرآیند به روش المان محدود نیز  بر روی این آلیاژ به منظور ارزیابی چگونگی تغییرات توزیع تنش و کرنش بر روی نمونه‌ها صورت پذیرفت. مشاهده گردید که بیشترین کرنش در قسمت‌های مرکزی نمونه‌ها رخ داده و نسبت به حالت تئوری دارای 0/25 درصد خطا می‌باشد. با مقایسه تنش تسلیم حاصل شده نسبت به روش شبیه سازی شده مشاهده گردید که میزان خطا 3/7 درصد است.

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of microstructure and mechanical properties of Al (A356) after processing by ECAP and its simulation

نویسندگان [English]

  • Hamid Mohajerani 1
  • Ahmad Afsari 2
1 MSc student / Mechanical Engineering Department, Islamic Azad University
2 Assistant Professor / Mechanical Engineering Department, Islamic Azad University
چکیده [English]

Equal channel angular pressing (ECAP) is one of the most important methods of severe plastic deformation for fabrication of ultrafine-grained metals and alloys. The aim of this research is to study the improvement and amendment of the microstructure and mechanical properties of aluminum alloy (A356) by ECAP, which has known applications in air-space industries. To achieve this aim, a die with channel contiguity angel of 120 and outer arc of curvature of 20 degrees were designed and fabricated. The process was applied at room temperature. Furthermore, the samples were annealed and the solution treatment was performed before the beginning of the process. Hardness, compression and tensile tests were applied on samples after the process was performed and microstructures of samples were evaluated by means of optical microscopy before and after the process. Mechanical properties of samples were studied and fracture surfaces of samples were characterized using scanning electron microscope (SEM). The results showed that hardness of the annealed sample was increased from 48 to 84.2 Vickers after 2 passes of ECAP and the results of the tensile test showed that the tensile strength was increased from 57 to 177 M.pa after 1 pass of ECAP. Finite element simulation method was utilized to estimate the variation of stress and strain distribution on the samples. The analyses indicated that the highest level of strain occurred on the center portions of samples and a minor (0.25 percent) error was detected in comparison to theoretical calculation of strain. Also, the experimental yield stress showed a small error of 3.7 percent compared to the values predicted by the simulation.

کلیدواژه‌ها [English]

  • ECAP
  • Aluminum alloy (A356)
  • Microstructure
  • Hardness
  • Tensile strength
  • Simulation
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