10118

9348

كارشناسي ارشد

شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1393

سيزده، 86ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

احمد كرمانپور، عباس نجفي زاده

3/3/94

محمدحسين عنايتي، احمد رضائيان

1396/10/02

كتابنامه

مواد

مهندسي مواد

ID9348

87 Evaluating the effect of niobium addition on microstructural evolutions and mechanical properties of an ultrafine nano grained dual phase steel by thermomechanical process Ali Ghatei Kalashami a ghatei@ma iut ac ir 14 Jan 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisors Ahmad Kermanpur Ahmad K@cc iut ac ir Abbas Najafizadeh a najafi@cc iut ac irAbstractsThe aim of this investigation is the evaluating the effect of niobium addition as amicroalloying element on microstructural evolutions and mechanical properties of anultrafine grained dual phase UFG DP steel For this purpose four steels with the samechemical composition and different Nb contents 0 00 0 06 0 12 and 0 18 wt wereproduced by the vacuum induction melting VIM process The UFG DP steels wereproduced utilizing simple cold rolling and subsequent intercritical annealing of a ferrite martensite duplex starting structure The duplex structure was cold rolled up to 80 thickness reduction followed by intercritical annealing at 770 C for 4 6 and 8 mins Results from microscopic images showed that increasing Nb content up to 0 12 wt increased the volume fraction of martensite and decreased the average grain size of ferrite however a lower martensite content with no further grain refinement was detected in thesteel containing 0 18 wt Nb at the intercritical annealing time of 6 and 8 mins Tensiletest revealed intense effect of Nb precipitations on improvement of mechanical properties The results illustrated an excellent strength elongation balance in terms of energyabsorption 160 Jcm 3 and toughness 229 MPa in comparison with the commerciallyused high strength steels The UFG DP steel containing 0 12 wt Nb showed highstrength about 123 higher than that of the ferritic pearlitic as received state e g 540MPa without loss of ductility The Hollomon Crussard Jaoul C J and modified C Janalyses were used to demonstrate the strain hardening behavior of DP steels The resultsshowed that the Hollomon and C J analyses proposed two stage deformation for presentDP steels while the modified C J analysis illustrated three stage deformation In all DPsteels the prominent mode of fracture is ductile Also it is found that the average dimplesize is decreased with increasing Nb content The variations of strength elongation strainhardening behavior and fracture mechanism of the specimens with Nb contents andintercritical annealing time were correlated to the microstructural features Keywords Ultrafine grained dual phase steel cold rolling and subsequent intercriticalannealing microalloying element niobium

احمد كرمانپور، عباس نجفي زاده

محمدحسين عنايتي، احمد رضائيان