Abstract
The decomposition of delta-ferrite and its effects on tensile properties and fracture of a hot-rolled AISI 304L stainless steel plate were studied. Magnetic response measurements of annealed specimens showed that the transformation rate of delta-ferrite was highest at 720 °C. Transformation behavior was characterized by light microscopy, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy on thin foils. The initial transformation of delta-ferrite (δ) to austenite (γ) and a chromium-rich carbide (M23C6) occurred by a lamellar eutectoid reaction, δ⇄M23C6 +γ. The extent of the reaction was limited by the low carbon content of the 304L plate, and the numerous, fine M23C6 particles of the eutectoid structure provide microvoid nucleation sites in tensile specimens annealed at 720 °C for short times. Sigma phase(σ) formed as a result of a second eutectoid reaction,δσ +γ. Brittle fracture associated with the plate-shaped sigma phase of the second eutectoid structure resulted in a significant decrease in reduction of area (RA) in the transverse tensile specimens. The RA for longitudinal specimens was not affected by the formation of sigma phase. Tensile strengths were little affected by delta-ferrite decomposition products in either longitudinal or transverse orientations.
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Y. Shen, formerly with the Department of Metallurgical and Materials Engineering, Colorado School of Mines, is deceased.
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Tseng, C.C., Shen, Y., Thompson, S.W. et al. Fracture and the formation of sigma phase, M23C6, and austenite from delta-ferrite in an AlSl 304L stainless steel. Metall Mater Trans A 25, 1147–1158 (1994). https://doi.org/10.1007/BF02652290
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DOI: https://doi.org/10.1007/BF02652290