7196

6702

كارشناسي ارشد

شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1391

چهارده، 88ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

عباس نجفي زاده، احمد كرمانپور

10/8/91

محمد حسين عنايتي، احمد رضائيان

1396/09/20

كتابنامه

مواد

مهندسي مواد

ID6702

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Evaluating Microstructure and Mechanical Properties of the Nano Ultrafine Grained Low Alloy Steel by Thermomechanical Treatment with Bainitic and Martensitic Starting Microstructures Reza Gostariani r gostariani@ma iut ac ir September 22 2012 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDrgree M Sc Language FarsSupervisors A Najafizadeh Prof a najafi@cc iut ac ir A Kermanpur Assoc Prof ahmad k@cc iut ac ir AbstractThe improvement of mechanical properties of steels is an important priority for industry Among different strengthening approaches grain refinement is the only method toimprove both strength and toughness simultaneously Martensite process including coldrolling and subsequent annealing of the microstructures with high percentage of martensiteis one of the effective methods for grain refinement in carbon steels In this research thisprocess was applied to the low alloy steel DIN1 5715 Brittle martensite microstructuresresulted in transverse cracks during rolling Therefore bainite microstructure with thesame formation mechanism could be the best candidate to replace the martensite Severalspecimens were heat treated to form high percentage of martensite and bainitemicrostructures Colour metallography was performed for determination of type andprecentage of phases before rolling The heat treated specimens were cold rolled with 90 reduction in thickness and then annealed at different times and temperatures Microstructure evolution was characterized using optical and scanning electronmicroscopes at the each stage of the process Mechanical properties of specimens weredetermined by hardness and uniaxial tensile test Microstructure of the annealed specimensin both martensite and bainite processes revealed a high fraction of ultrafine ferrite grainswith 100 nm and 300 nm respectively Mechanical properties of the ultrafine grainmicrostructures in the martensite and bainite processes showed tensile strength of1200MPa and 700MPa respectively This indicated sixfold and threefold improvementcompared with the initial structures The elongation of the ultrafine grained steel in thebainite process 20 was twice of the one produced in martensite process 9 Keywords Thermomechanical process martensite process bainite process cold rolling annealing

عباس نجفي زاده، احمد كرمانپور

محمد حسين عنايتي، احمد رضائيان