Phase Transformation Kinetics During Annealing of Cold-Rolled AISI 309Si Stainless Steel
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can be rationalized by the Md30 temperature, where Md30 is the deformation temperature at which 50 vol pct martensite forms by the application of true strain of 0.3 in tension[6]: Md30 ðKÞ ¼ 1097462ðC þ NÞ9:2Si8:1Mn13:7Cr 29ðNi þ CuÞ18:5Mo68Nb1:42ðGs8Þ;
½1 ATA ABDI, HAMED MIRZADEH, MOHAMMAD JAVAD SOHRABI, and MEYSAM NAGHIZADEH The effects of cold rolling and the subsequent annealing were studied for the AISI 309Si stainless steel. During annealing of cold-rolled sheets, the hardness curve vs temperature showed two regimes of transformations (reversion and recrystallization), where the JMAK analysis revealed that the activation energy of both processes is equal to the lattice diffusion activation energy in austenitic stainless steel. Finally, based on the kinetics analysis, a recrystallization–temperature–time diagram for phase transformations was proposed. https://doi.org/10.1007/s11661-020-05678-4 The Minerals, Metals & Materials Society and ASM International 2020
AISI 309Si (DIN 1.4828) is a heat-resistant Cr-Ni-Si stainless steel, which is widely used in high-temperature applications in chemical plants and for welding due to its excellent corrosion and oxidation resistance.[1] The latter is associated with the high Cr (19 to 21 wt pct) and Ni (11 to 13 wt pct) contents of this material, and from this standpoint, it shows a better performance compared to the more widely used grades such as AISI 304 stainless steel.[2] Like Cr and Al, the high Si content of this alloy (1.5 to 2.5 wt pct) can also improve oxidation or scaling resistance,[3–5] where the formation of the continuous silica layer as the diffusion barrier required a combination of fine alloy grain size and high Si content.[5] AISI 309Si alloy is expected to be more resistant against the strain-induced martensitic transformation (SIMT) compared to the metastable AISI 304 alloy due to the much higher alloying content in the former. This
ATA ABDI, HAMED MIRZADEH, MOHAMMAD JAVAD SOHRABI, and MEYSAM NAGHIZADEH are with the School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran. Contact e-mail: [email protected] Manuscript submitted December 24, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
where Gs is the ASTM grain size number. It has been reported that AISI 309 did not exhibit strain-induced transformation during room temperature tension.[7] Therefore, there is no report on the formation of martensite in AISI 309 grade and its reversion during subsequent annealing. Moreover, to the best of authors’ knowledge, there is no report on the cold rolling and primary recrystallization of this material, where the obtained grain refinement can be advantageous for both mechanical properties[8–12] and stronger passive film.[5,13] In response, the present work aims to study the phase transformation kinetics during annealing of cold-rolled AISI 309Si stainless steel. AISI 309Si stainless steel with chemical composition (wt pct) of Fe-0.05C-20.00Cr-11.50Ni-1.90Si-0.85Mn0.33Cu-0.30Mo,
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