حامد میرزاده
عضو هیات علمی دانشگاه تهران
[ 1 ] - کنترل ریزساختار و خواص مکانیکی فولاد زنگ نزن آستنیتی توسط بازگشت مارتنزیت کرنشی و تبلور مجدد آستنیت باقیمانده
تحولات ریز ساختاری در حین عملیات آنیل فولاد زنگ نزن آستنیتی 304 پس از نورد سرد مورد ارزیابی قرار گرفت و مشخص شد که سه مرحله مجزا وجود دارد که شامل بازگشت مارتنزیت به آستنیت، تبلور مجدد آستنیت باقی مانده و رشد دانه می‌باشد. بازگشت مارتنزیت به آستنیت منجر به تولید ساختار فوق ریزدانه شد. با این وجود، تبلور مجدد آستنیت باقی مانده، تشکیل ساختار هم محور را به تاخیر انداخت و سبب شد که دانه های ریز آست...
[ 2 ] - Improvement of Mechanical Properties and Work-Hardening Behavior of Intercritically Annealed Dual Phase Steel
The effect of the initial microstructure and intercritical annealing on mechanical properties and work-hardening response of a high-formability low carbon steel were studied. The work-hardening analysis was based on the modified Crussard–Jaoul method. The ferritic-pearlitic sheets showed low strength and high total elongation with the appearance of the yield point phenomenon. The occurrence of ...
[ 3 ] - Microstructural Evolution of Roll Bonded Al-Clad Stainless Steel Sheets at Elevated Temperatures
The cold roll bonding of Al on AISI 304L stainless steel was carried out to fabricate the Al/304L/Al clad sheet composites. The maximum bond strength of 20 N/mm was acquired just by 38% reduction, for which the tearing of the aluminum sheet occurred during the peeling test. The microstructural evolution during subsequent postannealing heat treatment was systematically studied based on the impur...
[ 4 ] - Grain Refinement of Dual Phase Steel via Tempering of Cold-Rolled Martensite
A microstructure consisting of ultrafine grained (UFG) ferrite with average grain size of ~ 0.7 µm and dispersed nano-sized carbides was produced by cold-rolling and tempering of the martensite starting microstructure in a low carbon steel. Subsequently, fine grained dual phase (DP) steel consisting of equiaxed ferrite grains with average size of ~ 5 µm and martensite islands with average size ...
[ 5 ] - Magnificent Grain Refinement of Al-Mg2Si Composite by Hot Rolling
The effect of chemical composition and the hot rolling operations on the microstructure and mechanical properties of in situ aluminum matrix composite with Mg2Si phase as the reinforcement was studied. It was revealed that the modification by phosphorous results in the rounder (more spherical) primary and secondary (eutectic) magnesium silicide intermetallics. During hot rolling, the primary pa...
[ 6 ] - Grain Refinement and Enhancement of Mechanical Properties of Hot Extruded Rare-Earth Containing Magnesium Alloy
The effects of rare earth addition and hot extrusion process on the grain refinement of magnesium alloy were studied. The as-cast Mg-6Al-1Zn (AZ61) alloy had the average grain size of ~ 64 µm and its microstructure consisted of α-Mg and Mg17Al12 phase. By partial substitution of Al with Gd to reach Mg-4.8Gd-1.2Al-1Zn alloy, it was observed that the Mg17Al12 phase disappeared and two new interme...
[ 7 ] - Accumulative Roll Bonding of Aluminum/Stainless Steel Sheets
An Al/Stainless Steel/Al lamellar composite was produced by roll bonding of the starting sheets at 400 °C. Afterward, the roll bonded sheet was cut in half and the accumulative roll bonding (ARB) process at room temperature was applied seven times. As a result, the central steel layer fractured and distributed in the Al matrix among different layers introduced by the repetition of roll bonding ...
[ 8 ] - Grain Refinement Efficiency of Multi-Axial Incremental Forging and Shearing: A Crystal Plasticity Analysis
Severe plastic deformation is a technical method to produce functional material with special properties such as high strength and specific physical properties. Selection of an efficient severe plastic deformation for grain refinement is a challenging field of study and using a modeling technique to predict the refinement efficiency has gained a lot of attentions. A comparative study was carried...
[ 9 ] - Unraveling the Effects of Process Control Agents on Mechanical Alloying of Nanostructured Cu-Fe Alloy
Nanostructured Cu-20Fe alloy was synthesized by mechanical alloying process and the effects of process control agents (PCA) on the phase formation, crystallite refinement and morphology of powder particles were studied. The dissolution of Fe into Cu matrix and the morphology of powder particles were analyzed by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), respective...
[ 10 ] - Martensite phase reversion-induced nano/ ultrafine grained AISI 304L stainless steel with magnificent mechanical properties
Austenitic stainless steels are extensively used in various applications requiring good corrosion resistance and formability. In the current study, the formation of nano/ ultrafine grained austenitic microstructure in a microalloyed AISI 304L stainless steel was investigated by the advanced thermomechanical process of reversion of strain-induced martensite. For this purpose, samples were subjec...
[ 11 ] - معادله رفتاری پایه فیزیکی برای پیش بینی تنش سیلان فولاد میکروآلیاژی در حین تغییرشکل داغ
معادلات رفتاری بر پایه مکانیک نابجایی ها در دماهای نسبتا پایین قابل استفاده هستند. اما برای مدل کردن تنش سیلان در دماهای بالا، نیاز به در نظر گرفتن فرآیندهای نفوذی می باشد. به عبارتی، اثر نرم شوندگی بازیابی و تبلور مجدد دینامیکی باید درنظر گرفته شود. در تحقیق حاضر، یک معادله رفتاری اصلاح شده زریلی-آرم استرانگ برای پیش بینی تنش سیلان دمای بالای یک فولاد میکروآلیاژی ارایه شد که در آن اثرات سخت شو...
[ 12 ] - Processing of Fine-Grained DP300/600 Dual Phase Steel from St12 Structural Steel by the Thermo-Mechanical Processing of Cold Rolling and Intercritical Annealing
The effect of microstructural refinement and intercritical annealing on the mechanical properties and work-hardening response of a low carbon St12 steel was studied. It was revealed that intercritical annealing of the ferritic-pearlitic sheet results in the formation of a coarse-grained DP microstructure with discrete martensite islands normally formed in place of pearlitic colonies, which resu...
[ 13 ] - Enhancement of mechanical properties of low carbon steel based on heat treatment and thermo-mechanical processing routes
Thermal treatments and thermo-mechanical processing routes were applied on a conventional structural steel (st37 steel: 0.12C-1.11Mn-0.16Si) for improvement of tensile properties and enhancement of work-hardening behavior. Full annealing resulted in a sheet with coarse ferrite grains and pearlite colonies arranged alternatively in distinct bands, which showed high ductility, low strength, and t...
[ 14 ] - سینتیک رشد دانه در آلیاژهای منیزیم حاوی آلومینیوم و عنصر نادر خاکی گادولینیم
Microstructural evolutions during the high-temperature annealing of Mg alloys containing Al and Gd and after the extrusion process were evaluated and compared to those of the AZ61 alloy. It was revealed that during exposure at the elevated temperatures, the presence of (Mg,Al)3Gd phase, in the form of fine and dispersed particles in the matrix after the extrusion process, could be favorable for...
[ 15 ] - Computational evaluation of the homogeneity of composites processed by accumulative roll bonding (ARB)
A new computational method based on MATLAB was used to study the effect of different parameters on the homogeneity of composites produced by a severe plastic deformation technique known as accumulative roll bonding. For a higher number of passes, the degree of particle agglomeration and clustering decreased, and an appreciable homogeneity was obtained in both longitudinal and transverse directi...
[ 16 ] - Quantifying the dependency of uniform corrosion of structural steel on grain size
The dependency of uniform corrosion of structural steel on the average grain size (D) should be quantified for design purposes. In the present work, a spectrum of grain sizes was obtained by simple heat treatment routes in st37 structural steel. It was revealed that the corrosion current density (icorr) increased by grain refinement, which was related to the increased density of grain boundarie...
[ 17 ] - بررسی ریزساختار سوپرآلیاژ اینکونل 718 در حالت های ریختگی و همگن سازی شده
ریزساختار سوپرآلیاژ اینکونل 718 در حالت‌های ریخته شده (ذوب مجدد در قوس الکتریکی تحت خلاء و انجماد در قالب مسی آبگرد) و همگن سازی شده مورد تحلیل و بررسی قرار گرفت. جهت مطالعه ریزساختار و تجزیه و تحلیل عنصری، میکروسکوپ الکترونی روبشی و روش طیف سنجی پراکندگی انرژی استفاده شد. حضور ساختار یوتکتیک آستنیت / فاز لاوه و کاربیدها بر اساس نمودار فازی و ریزجدایش عناصر نیوبیوم و مولیبدن بین بازوهای دندریت...
[ 18 ] - Controlling the Mechanical Properties and Corrosion Resistance of Mild Steel by Intercritical Annealing and Subcritical Tempering
The effects of intercritical annealing and subcritical tempering on the mechanical properties and corrosion resistance of mild steel were studied. It was revealed that intercritical annealing followed by quenching resulted in the development of a ferritic-martensitic dual phase (DP) microstructure with high tensile strength, disappearance of the yield-point phenomenon, superior work-hardening b...
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