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Öğe Chemical Composition Optimization and Isothermal Transformation of ?-Transformation-Induced Plasticity Steel for the Third-Generation Advanced High-Strength Steel Grade(Wiley-V C H Verlag Gmbh, 2024) Okur, Onur; Davut, Kemal; Palumbo, Gianfranco; Nalcaci, Burak; Guglielmi, Pasquale; Yalcin, Mustafa Alp; Calin, RecepA new low-manganese transformation-induced plasticity steel is designed with optimized nickel content to achieve superior strength and ductility while minimizing the use of expensive nickel. The steel is optimized using JMatPro software, then cast, and hot rolled. To assess the effect of intercritical annealing on austenite (martensite at room temperature) volume fraction and carbon content, hot-rolled steel samples quenched from different annealing temperatures (680-1100 degrees C) are used. Additionally, hot-rolled steel coupons are intercritically annealed at about 50% austenite formation temperature (740 degrees C) and then subjected to isothermal treatments at 300-425 degrees C for varying times (10-90 min). After optimizing these treatments to maximize retained austenite (RA), tensile specimens are heat-treated first at 740 degrees C and then isothermally at 325 degrees C. Thermodynamic calculations suggest that aluminum combined with silicon may lead to the delta ferrite formation, and even minimal nickel content can stabilize a considerable amount of austenite. In the experimental studies, it is shown that lower-temperature bainitic holding enhances austenite stability by enriching the carbon content. Optimized two-stage heat treatments yield up to 25.8% RA, with a tensile strength of 867.2 MPa and elongation of 40.6%, achieving a strength-elongation product of 35.2 GPax%, surpassing the third-generation advanced high-strength steel grades minimum requirement of 30 GPax%.Öğe Correction: Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron (International Journal of Metalcasting, (2022), 16, 4, (1836-1848), 10.1007/s40962-021-00723-3)(Springer Science and Business Media Deutschland GmbH, 2023) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, MehmetThe original online version of this article was revised. The graphical abstract, Fig. 8, Table 4, and miscellaneous values throughout the text were corrected. © 2023, American Foundry Society.Öğe Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron(Springer Science and Business Media Deutschland GmbH, 2022) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, MehmetThe present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu–Ni–Mo-alloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 °C for the duration of 15–30–60 min followed by holding in a salt bath at an austempering temperature of 260 °C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. Graphical Abstract: [Figure not available: see fulltext.] © 2021, American Foundry Society.Öğe EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON(Springer Int Publ Ag, 2022) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, MuratThe present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu-Ni-Moalloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 degrees C for the duration of 15-30-60 min followed by holding in a salt bath at an austempering temperature of 260 degrees C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. [GRAPHICS] .Öğe EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON (vol 16, pg 1836, 2021)(Springer Int Publ Ag, 2023) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat[Abstract No tAvailable]
