نوع مقاله : مقاله کامل پژوهشی
نویسندگان
دانشکده مهندسی مواد و صنایع، دانشگاه صنعتی نوشیروانی بابل، بابل، ایران.
چکیده
آلیاژهای منیزیمی، به دلیل استحکام مناسب، مدول یانگ و چگالی شبیه به استخوان انسان، دارای کاربردهای پزشکی بالقوهای در حوزه کاشتنی های زیست تخریب پذیر هستند. با این حال، یکی از مهم ترین موانع کلیدی برای کاربردهای بالینی آلیاژهای منیزیم، خوردگی سریع این آلیاژها در محیط بدن انسان است. اصلاح دانه ناشی از فرآیند حرارتی- مکانیکی، یک روش موثر برای افزایش استحکام و شکل پذیری آلیاژهای منیزیم بوده و ممکن است مقاومت به خوردگی آلیاژهای منیزیمی را تحت تاثیر قرار دهد. از این رو، در این پژوهش تاثیر فرآیند حرارتی- مکانیکی (شامل پرس گرم در دمای C˚ 250 و سپس عملیات حرارتی آنیل به مدت یک ساعت در دمای C˚ 300) بر رفتار خوردگی آلیاژ منیزیمی AZ31 پس از یک، چهار و هفت روز غوطه وری در محلول شبیه سازی شده بدن در دمای C˚ 25، مورد بررسی قرار گرفت. برای بررسی ریزساختار نمونه ها از میکروسکوپ نوری و الکترونی و از آزمون قطبش و مقاومت ظاهری الکتروشیمیایی به ترتیب برای ارزیابی نرخ خوردگی و مقاومت به خوردگی استفاده گردید. بررسی ریزساختار نمونه ها، نشان داد که عملیات حرارتی- مکانیکی موجب اصلاح دانه و بروز دوقلویی ها گردید. تبلور مجدد حاصل از فرآیند حرارتی- مکانیکی موجب ریز شدن دانه ها، افزایش مرزهای دانه و کاهش چگالی نابجایی ها شد که به نوبه خود مانع گسترش خوردگی می شوند. نتایج حاصل از آزمون های مقاومت ظاهری و قطبش نیز نشان داد که میزان مقاومت به خوردگی نمونه AZ31 تحت عملیات حرارتی- مکانیکی، پس از هفت روز غوطه وری، افزایش و نرخ خوردگی آن کاهش یافته است.
کلیدواژه‌ها
عنوان مقاله [English]
The Effect of Thermomechanical Process on the Corrosion Behavior of AZ31 Magnesium Alloy in Simulated Body Fluid
نویسندگان [English]
- Hamed Jafari
- Seyed Mahmood Rabiee
- Seyed Jamal Hosseinipour
Faculty of Materials and Industrial Engineering, Babol Noshirvani University of Technology, Babol, Iran.
چکیده [English]
Magnesium alloys, with suitable strength, human-like elastic modulus and density, have potential medical applications in the field of biodegradable implant materials. However, one of the most important barriers to clinical applications of magnesium alloys is the rapid corrosion of these alloys in human body fluids. Grain refinement is an effective way to increase the strength and ductility of magnesium alloys and may improve the corrosion resistance of them. Grain refinement due to the thermomechanical process is an effective way to increase the strength and ductility of magnesium alloys and may affect the corrosion resistance of magnesium alloys. Hence, in this study, the effect of thermomechanical process (including warm forging at 250 ˚C and then annealing for 1 hour at 300 ˚C) on the corrosion behaviour of AZ31 magnesium alloy after 1, 4 and 7 days of immersion in a simulated body fluid was investigated at 25 ˚C. To investigate the microstructure of the samples, an optical and scanning electron microscopes were used. The electrochemical polarization and impedance tests were used to evaluate corrosion rate and corrosion resistance, respectively. The microstructure analysis of the samples showed that the thermomechanical process refined the grain and caused the twins to appear. In fact, the recrystallization resulting from the thermomechanical process caused the grain to refine, increasing the grain boundaries, and reducing the dislocations density, which, in turn, prevented corrosion. The results of impedance and polarization tests also showed that the corrosion resistance of AZ31 sample under thermomechanical operation increased after 7 days of immersion and decreased its corrosion rate.
کلیدواژه‌ها [English]
- Thermomechanical
- Corrosion rate
- AZ31 alloy
- Microstructure
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