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1 - Mechanical Behavior of Al-SiCnp Nanocomposite Fabricated by Hot Extrusion Technique
A. Atrian S. H. NourbakhshIn this paper, fabrication and characterization of Al-SiC nanocomposites is investigated. The Al matrix is reinforced with different amounts of SiC nano-particles using mechanical milling, cold pressing, and, hot extrusion techniques. To get the best quality of the samp أکثرIn this paper, fabrication and characterization of Al-SiC nanocomposites is investigated. The Al matrix is reinforced with different amounts of SiC nano-particles using mechanical milling, cold pressing, and, hot extrusion techniques. To get the best quality of the samples, the extrusion process is optimized firstly. With this regard, hot extrusion parameters such as the rate of extrusion, temperature, the extrusion ratio, lubrication, and the die set dimensions are experimentally studied. Finally, the nanocomposites with relative density more than 99% could be successfully fabricated under extrusion ratio of 8.5:1. As-extruded billets were then used to prepare standard tensile test specimens based on ASTM-E8. Afterwards, relative density, tensile behaviour, and micro-hardness of the samples were determined. The results show about 50% improvement for both the tensile strength and micro-hardness and near 1% reduction of relative density as the content of SiC reinforcement increases to 3 vol%. Therefore, specimens with higher strength-to-weight ratio which is a key parameter in aerospace and automotive applications can be produced using current techniques. تفاصيل المقالة -
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2 - The Effect of Sintering and Compaction Conditions on the Microstructure and Properties of AZ31 Magnesium Alloy
amin saghafi Seyed Ehsan Eftekhari Shahri Hossein Jamshidi Mohammad Kazem Salari Razieh KhoshhalMagnesium and its alloys are attractive materials in industrial applications due to the low density and high strength. The properties of AZ31 magnesium alloy can be much improved by choosing proper sintering conditions. In this study, the microstructure and mechanical p أکثرMagnesium and its alloys are attractive materials in industrial applications due to the low density and high strength. The properties of AZ31 magnesium alloy can be much improved by choosing proper sintering conditions. In this study, the microstructure and mechanical properties of AZ31 prepared by mechanical alloying, compaction, and sintering of elemental powder, were studied. The effect of parameters such as compaction pressure, heating rate, and sintering time were investigated to determine the optimal sintering condition of AZ31 magnesium alloys. Previous researches have focused on the specific conditions of sintering, while in this study, various factors of sintering were examined simultaneously. The results showed that sintering time is one of the major variables that have a considerable effect on the final properties of AZ31. In short sintering times, recrystallization leads to small grain formation inside the powder. However, as the sintering time increases, the growth of new grains slows down and no trace of them can be detected in the microstructure. Furthermore, the conditions for recrystallization were also determined, which can be used to provide small grain size and, consequently, better properties after the initial powder milling and sintering. At optimal sintering conditions, the average grain size, porosity percentage and hardness of the samples AZ31 magnesium alloy were obtained as 104 µm and 2.05%, and 79.5 HV, respectively which is expectable result in comparison to the bulk AZ31. تفاصيل المقالة -
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3 - Fabrication and characterization of the Ti-6Al-4V/Mg scaffold
Seyed Kalantari Hossein Arabi Shamsodin Mirdamadi Seyed MirsalehiTi–6Al–4V scaffolds were fabricated by powder metallurgical space holder technique in this research. The most added magnesium (Mg) powder was evaporated and a skeleton of Ti-6Al-4V alloy was produced. For this purpose Ti-6Al-4V and Mg powders mixture compact أکثرTi–6Al–4V scaffolds were fabricated by powder metallurgical space holder technique in this research. The most added magnesium (Mg) powder was evaporated and a skeleton of Ti-6Al-4V alloy was produced. For this purpose Ti-6Al-4V and Mg powders mixture compacted in a steel die by applying uniaxial pressure of 500 MPa before sintering the green product in a sealed quartz tubes at 900 °C for 2 hours. Employing Archimedes’ principle and an Image Tool software, the total and open volume percent of porosities within the scaffolds were found to be in the range of 46-64% and 41-47%, respectively. Bioactivity properties of the scaffolds were investigated in a simulated body fluid (SBF). Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) were used for studying the specimens’ surfaces after immersing them for 28 days. The results showed that the amounts of calcium (Ca) and phosphor (P) deposited into the porous areas were more than that of smooth surfaces due to the presence of Mg particles within the pores which provoked formation of apatite layers. Changing in the pH values of the SBF during 18 days of immersion revealed that gradual improvement in pH level due to releasing OHˉ .Using atomic absorption spectroscopy (AAS) indicated that by increasing Mg content of scaffolds, Ca concentration of SBF decreased which is an indication of apatite formation on the scaffold. Results of SBF bioactivity assays exhibited that the scaffold with 60 vol.% Mg has the best ability to induce apatite nucleation. تفاصيل المقالة -
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4 - Effects of Friction Stir Process Parameters on Microstructure and Mechanical properties of Aluminum Powder Metallurgy Parts
Mohsen Abbasi-Baharanchi Fathallah Karimzadeh Mohammad Hossein EnayatiThe effects of friction stir processing (FSP) on the microstructure and mechanical properties of aluminum powder metallurgy (PM) parts was investigated. PM parts were then subjected to FSP at advancing speeds (v) of 40-200 mm/min and tool rotational speeds (ω) of أکثرThe effects of friction stir processing (FSP) on the microstructure and mechanical properties of aluminum powder metallurgy (PM) parts was investigated. PM parts were then subjected to FSP at advancing speeds (v) of 40-200 mm/min and tool rotational speeds (ω) of 800-1600 rpm. Microhardness (HV) and tensile tests at room temperature were used to evaluate the mechanical properties of the friction stir processed specimens. In order to evaluate microstructure of processed zone, cross-sections of FS processed specimens were observed optically. Based on the results obtained from investigation of the Zener-Holloman parameter (Z), average grain size decreased with decreasing working temperature and increasing working strain rate (equal to increasing Z). The finest grain size was ~ 5.4µm obtained at ω=1000 and v =100 mm/min corresponding to a strain rate of 27s-1 at 414 . This sample exhibited, the best mechanical properties with microhardness, yield stress, and tensile strength of the 43 Hv, 82 MPa, and 118.3 MPa, respectively. تفاصيل المقالة -
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5 - Effect of Zn and porosity on the biodegradability and Mechanical Properties of Mg-Zn Scaffolds
zahra sadat seyedraoufiIn the present research porous Mg-Zn scaffolds with different Zn amount and porosities were synthesized by powder metallurgy process as potential degradable materials for orthopedic applications. The microstructures, composition, mechanical properties and in vitro biode أکثرIn the present research porous Mg-Zn scaffolds with different Zn amount and porosities were synthesized by powder metallurgy process as potential degradable materials for orthopedic applications. The microstructures, composition, mechanical properties and in vitro biodegradability of the scaffolds were investigated. Optic microscopy (OM) images showed that the Mg-Zn scaffolds exhibit homogeneously distributed and interconnected pores with the size of about 150–400 µm. The X-ray diffractometer (XRD) results indicated the formed intermetallics consist of Mg12Zn13 and Mg51Zn20 in the Mg matrix. Compressive tests showed that decrease of porosity and the addition of Zn increases the compressive strength of specimens. Electrochemical tests indicated that with increase of porosity, the corrosion current density of scaffolds increased and Mg-Zn scaffolds synthesized improved the in vitro biodegradability property of the Mg; the best biodegradability property was obtained with 3% Zn and the porosity of about 7% ; further increase of Zn content up 4% deteriorates biodegradability. It is found that the products of immersion in simulated body fluid (SBF) are identified to be HAP, (Ca,Mg)3(PO4)2 and Mg(OH)2 and MG63 cells adhere and proliferate on the surface of the scaffolds, making them a promising choice for orthopedic application. تفاصيل المقالة -
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6 - Comparison of ZAMAK 2 and ZAMAK 3 Alloys Produced by Powder Metallurgy Process
Abdolhamid Azizi Gholamali Gheiratmand Haghighi Pooya Bahrami Sahebali ManafiThe predominant method to produce ZAMAK alloys is casting. But this process is not without flaws. Factors such as low melting temperature, creep stresses, aging, and dimension change over time are the main problems in ZAMAK’s casting process. We embarked on this r أکثرThe predominant method to produce ZAMAK alloys is casting. But this process is not without flaws. Factors such as low melting temperature, creep stresses, aging, and dimension change over time are the main problems in ZAMAK’s casting process. We embarked on this research to investigate the new production routes. In this regard, the powder metallurgy can be highlighted because of the non-occurrence of melting and non-solid-liquid phase changes. ZAMAK 2 and 3 are the most commonly used ZAMAK alloys. In this way, we study the comparison of ZAMAK 2 and 3 produced by powder metallurgy. The powder was prepared by the mechanical method. As we proceed, the effect of particle size, pressure, and sintering temperature will be investigated. The comparison was done in consideration of mechanical properties such as density, tensile strength, and hardness. The density of ZAMAK 2 obtained by the powder metallurgy method increases with increasing working pressure up to 400 MPa, but after this pressure, little change in density is observed. While in ZAMAK 3 the density increases with increasing pressure. The maximum ultimate stress obtained in ZAMAK 2 is approximately equal to 300 MPa, while, it is equal to 230 MPa for ZAMAK 3. In ZAMAK 2, we will see a 16.7% increase in density by selecting fine grains, but in Zamak 3, this enhancement is only equal to 7%, which indicates the intensive effect of particle size on the density obtained in ZAMAK 2. تفاصيل المقالة -
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7 - Survey of AZ31/HA-Zeolite Nano Crystalline Biocomposite with Powder Metallurgy (PM)
Mehrdad Soltani Ebrahim Karamian Majid KarimianMagnesium is potentially useful for orthopedic and cardiovascular applications. Magnesium and its alloys are light, biodegradable, biocompatible metals that have promising applications as biomaterials. However, the corrosion rate of this metal is so high that its degrad أکثرMagnesium is potentially useful for orthopedic and cardiovascular applications. Magnesium and its alloys are light, biodegradable, biocompatible metals that have promising applications as biomaterials. However, the corrosion rate of this metal is so high that its degradation occurs before the end of the healing process. One of the ways to improve the corrosion rate is to compose it with ceramic materials such as HA, TCP and so on. In this study, at first, the alloy with a nominal composition of Mg-3%Al-1%Zn (AZ31 alloy) was produced by high energy ball milling (HEBM) of Mg powder, Zn powder and Al powder under high purity argon. The ball milling parameters were chosen as following: shaft rotation was 600 rpm, ratio of balls to powder was 10:1 and milling time was 90, 180, 270 and 360 min under argon atmosphere. The obtained Mg alloy powders were pressed with different amounts of HA-Zeolite (HZ) powder mixture, weight ratio HA (Hydroxyapatite) to Zeolite 4:1, under 1000 MPa in steel die with 12 mm in diameter and 20 mm in height. The pressed samples were sintered for 1 h at 630 K in an inert atmosphere furnace. Microstructure characterization of as-milled powders and as-sintered alloys were carried out by SEM. An X-ray diffraction (XRD) was used for phase analysis. XRD patterns of the powders mixture showed that the AZ31 alloy powder has been gained after 270 min. تفاصيل المقالة -
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8 - تاثیر اندازه و نوع پوشش ذرات پودر آهن و میزان مس افزودنی بر ویژگیهای گویهای توخالی فولادی
حمید سازگاران علیرضا کیانی رشیدگویهای توخالی فلزی میتوانند به صورت موفقیتآمیز برای ایجاد سلولها و حفرات در ساختارهای سلولی و فومهای فلزی به کار گرفته شوند که مهمترین روشهای تولید آنها بر پایه متالورژی پودر استوار میباشد. در این پژوهش، گویهای توخالی فولادی با استفاده از دانههای پلیاستیرن ب أکثرگویهای توخالی فلزی میتوانند به صورت موفقیتآمیز برای ایجاد سلولها و حفرات در ساختارهای سلولی و فومهای فلزی به کار گرفته شوند که مهمترین روشهای تولید آنها بر پایه متالورژی پودر استوار میباشد. در این پژوهش، گویهای توخالی فولادی با استفاده از دانههای پلیاستیرن به عنوان ماده زیرلایه و به روش متالورژی پودر تولید شدند. دانههای پلیاستیرن از یک بلوک پلیاستیرن جدا شدند و دانهبندی آنها به اندازههای متفاوت توسط الک صورت گرفت. سپس، مخلوط سیلیکات سدیم به عنوان چسب و پودر آهن، بر روی دانههای تهیه شده پاشیده شد و پس از آغشته شدن دانهها به صورت کامل، خشک شدن درون هوا صورت گرفت. بنابراین، یک لایه نازک از پودرهای آهن به همراه چسب بر روی دانههای پلیاستیرن ایجاد شد. در پایان، دو فرآیند عملیات حرارتی مجزا به منظور تولید گویهای توخالی فولادی با استحکام بالا انجام شد که شامل تجزیه حرارتی دانههای پلیاستیرن و تفجوشی میباشد. به منظور ارزیابی ضخامت و میزان تخلخل پوسته گویهای توخالی فولادی و بررسی معایب آنها، مقاطع پوستهها توسط میکروسکوپ نوری مورد مطالعه قرار گرفت. گویهای توخالی فولادی تقریباً دارای ضخامت یکنواخت میباشند. اندازه دانههای پودر آهن، افزودنی مس و نوع پوشش پودرهای آهن تاثیر زیادی بر روی ضخامت، کسر سطحی تخلخل، ترکها و حفرات در پوسته دارند. تفاصيل المقالة -
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9 - مشخصه یابی کامپوزیت مس زیرکونیای پایدار شده با ایتریا تولید شده با تفجوشی پلاسمای جرقه ای
جعفر میرعظیمی پروین عباچی کاظم پورآذرنگ وحید باباییدرکاربردهایی مانند اتصالات الکتریکی کشویی، علاوه بر خواص مکانیکی قابل قبول به هدایت الکتریکی و حرارتی خوب نیاز است. گذشته از این، در این نوع کاربردها باید از جوش موضعی قسمتهای مختلف قطعه جلوگیری شود. اگرچه افزودن ذرات سرامیکی به فلز هادی الکتریکی و حرارتی همچون مس موجب أکثردرکاربردهایی مانند اتصالات الکتریکی کشویی، علاوه بر خواص مکانیکی قابل قبول به هدایت الکتریکی و حرارتی خوب نیاز است. گذشته از این، در این نوع کاربردها باید از جوش موضعی قسمتهای مختلف قطعه جلوگیری شود. اگرچه افزودن ذرات سرامیکی به فلز هادی الکتریکی و حرارتی همچون مس موجب کاهش خواص فیزیکی فوق میشود، تولید کامپوزیتهای زمینه مسی بهبود استحکام کششی، مقاومت سایشی و مقاومت در برابر جریان الکتریکی با آمپر بالا را در پی دارد. از این رو، در پژوهش حاضر کامپوزیتهای پایه مس حاوی 2، 3 و 5 درصد حجمی ذرات فوق ریزدانه زیرکونیای پایدار شده با ایتریا با استفاده از روش متالورژی پودر و تفجوشی پلاسمای جرقهای تولید شد. چگونگی توزیع ذرات تقویتکننده در ریز ساختار با استفاده از میکروسکوپ الکترونی به دقت مطالعه شد. مقادیر چگالی و سختی برینل اندازهگیری و هدایت حرارتی نمونهها تعیین شد. بر اساس نتایج، ذرات تقویتکننده به صورت قابل قبولی در زمینه توزیع شدهاند و خوشهای شدن ذرات در ریزساختار چندان فاحش نیست. چگالی نسبی بیشتر از 95% به علت نحوه تفجوشی برای همه نمونهها بدست آمد. به دلیل حضور ذرات سرامیکی سخت زیرکونیای پایدار شده، افزایش 60 درصدی در سختی برینل نمونهی کامپوزیتی Cu-5 vol.% YSZ نسبت به نمونه مس تقویتنشده مشاهده شد. همچنین، با افزایش مقدار زیرکونیای پایدار شده از صفر به 5 درصد حجمی، مقادیر هدایت حرارتی تعیین شده از 397 به W/m K 241 کاهش یافت که این تغییرات میتواند به مشخصههای ریزساختاری از جمله درصد فاز تقویتکننده، درصد تخلخل، وجود ناخالصیها و سایر عیوب ریزساختاری مربوط باشد. تفاصيل المقالة -
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10 - Producing the titanium nano composite statically compacted with the different pressure and investigation of the mechanical properties
سید مهران زحلی فرزاد فریباBuilding the Nano composites for getting material with combinational properties and improving properties of currently used material has been taken significant attention. One of the ways of building Nano composites is using a method known as powder metallurgy. Because wi أکثرBuilding the Nano composites for getting material with combinational properties and improving properties of currently used material has been taken significant attention. One of the ways of building Nano composites is using a method known as powder metallurgy. Because with this method not only wastes are decreased to minimum but we can also mix the materials with high melting point with the materials with low melting point which is a difficult thing to do with foundry method. In this research titanium alloy for improvement in its mechanical properties is mixed with silicon carbide reinforcing. Knowing the fact that silicon carbide is in Nano scale these two materials start building Nano composites. The powder metallurgy method is the best way for mixing these two materials together. To make sure that the properties of the made alloy is similar to the foundry alloy, the static compression methods are used. For comparison the results, two factors such as the Nano silicon carbide percentage and the static compression pressure are. Also, Density experiment, observation of grain boundaries using a scanning electron microscope, pressure test and the hardness experiment was done on it. تفاصيل المقالة
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