14605

1381 دكتري

دكتري

مهندسي مواد

اصفهان : دانشگاه صنعتي اصفهان

1397

نه، 117ص. : مصور، جدول، نمودار

احمد كرمانپور، عباس نجفي زاده

عباس اكبرزاده، محمدرضا طرقي نژاد، احمد رضائيان

1398/02/18

كتابنامه

مهندسي مواد

مهندسي مواد

1398/02/18

2527346

AbstractMicrostructures and mechanical properties of a new grade of Fe 18Cr 12Mn CN wt austenitic stainless steels interstitial alloyed with 0 3 to 0 48 wt C N at 0 22 to 1 06 C Nratios were investigated after thermomechanical processing Appropriatethermomechanical treatment was designed to obtain good combination of strength andelongation The developed steel possessed ultimate tensile strength of 1 GPa yield strengthof 450 MPa and elongation up to 83 It was found that strength and ductility of thestudied steels were affected by strain hardening behavior and decreasing the strain hardening rate resulted in lower ultimate tensile strength Addition of C to N containingNi free steels deteriorated mechanical properties The best combination of strength andelongation was obtained in steel with lowest C N 0 3wt and C N ratio 0 22 The martensite reversion treatment was conducted on two grades of Ni free austeniticstainless steels interstitially alloyed with C and N The hot rolled sheets of steels were coldrolled up to 80 thickness reduction to acquire strain induced martensite andsubsequently reversion annealed at temperatures from 700 to 850 C for 1 to 1000 s torevert the martensite to austenite Microstructural evolution was investigated usingoptical microscopy X ray diffraction electron backscatter diffraction and magneticmeasurement techniques Mechanical properties were measured using tensile tests at roomtemperature The resultant microstructures contained both reverted and recrystallizedaustenite when reverted at 700 and 750 C with the annealing time less than 100 s Anonuniform grain structure was characterized under these conditions consisting ofnano ultrafine grains formed via martensite reversion and coarser grains byrecrystallization of the retained austenite However a more uniform austenite grain sizewith average size of 1 m was obtained at 850 C for 1000 s The specimens havingnonuniform grain structure exhibited excellent combinations of strength and ductility Avariety of mechanical properties was achieved depending on the annealing condition Thework hardening behavior affected UTS and ductility of the studied steels The shift of thework hardening peaks to the higher strains was found suitable for ductility Addition of Cto N containing Ni free steels deteriorated mechanical properties Best combination ofstrength and elongation was obtained in the test material with lower C N ratio KeywordsInterstitially alloyed austenitic stainless steel Ni free stainless steel reversion annealing recrystallization mechanical properties nano ultrafine grain size

احمد كرمانپور، عباس نجفي زاده

عباس اكبرزاده، محمدرضا طرقي نژاد، احمد رضائيان