4702

4421

كارشناسي ارشد

شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1388

هشت،87،[II]ص.: مصور، نمودار

ص.ع.به فارسي و انگليسي

احمد كرمانپور،عباس نجفي زاده

3/8/88

رامين ابراهيمي، محمدرضا طرقي نژاد

1396/09/20

كتابنامه

مهندسي مواد

ID4421

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Investigating Microstructure and Mechanical Properties of a Nanostructured Low Carbon Steel by the Cold Rolling Annealing Process Student s Full Name Ehsan Ghassemali Email Address ehsan ghassemali@gmail com Date of Submission February 19 2009 Department of Materials Engineering Isfahan University of Technology Isfahan 84159 83111 IranDegree M Sc Language FarsiSupervisor s Name and Email Address Dr Ahmad Kermanpur ahmad k@cc iut ac irProf Abbas Najafizadeh a najafi@cc iut ac irAbstractCold rolling and subsequent annealing processing of low carbon steels is one of the advanced thermomechanicalprocessing which used for the production of nano grained microstructure In this work after quenching the lowcarbon 0 13 wt C steel was cold rolled up to 90 reductions of thickness The cold rolled specimens wereannealed at different temperatures for investigating the evolution of microstructure The microstructural changes occurring during the annealing were characterized by optical scanning electron and transmission electron microscope In addition color metallography method was used for determining theamount of martensite phase Kikuchi line analysis was employed for determining the miss orientation of grainboundaries The mechanical properties and fracture surface of the steel were studied Also the restorationkinetics of the low carbon steel during annealing of martensite process was investigated using JMAK model Results showed that fragmentation of martensite lathes during cold rolling of the quenched steels plays a keyrole in increasing the nucleation sites for recrystallization The mean grain size of about 188 4 200 3 and230 4 nm were achieved after annealing of the 90 80 and 70 cold rolled steel at 450 500 and 550 C respectively The final microstructure was composed of nano grained ferrite carbide precipitations and blocksof tempered martensite The major amount of grain boundaries are high angle boundaries type in the finalspecimens The mechanical properties of the nano grained steels increased up to 4 amplitudes with the properincrease of toughness Scanning electron microscopy investigations showed the ductile fracture mode with theshear dimples in fracture surfaces of the nano grained low carbon steels The JMAK model was expressed interms of hardness data from which the parameters of the different restoration kinetics were determined Thevalues of JMAK exponent n and the activation energy Q for recovery recrystallization and grain growth wereobtained for the steel under investigation Key WordsLow carbon steel Cold rolling Annealing Nanostructured Recrystallization Restorationkinetics

احمد كرمانپور،عباس نجفي زاده

رامين ابراهيمي، محمدرضا طرقي نژاد