首页|(105860)An investigation into the role of non-metallic inclusions in cleavage fracture of medium carbon peariitic steels for high-speed railway wheel
(105860)An investigation into the role of non-metallic inclusions in cleavage fracture of medium carbon peariitic steels for high-speed railway wheel
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NSTL
Elsevier
Non-metallic inclusions are often considered to be detrimental to the toughness of steels. Here, we found that, in a cleavage-dominated fracture mode, the toughness, particularly the room temperature fracture toughness of peariitic wheel steel can be improved by refining oxide inclusions or by increasing sulfur content. The roles of these inclusions in crack initiation and propagation were carefully investigated. Intriguingly, no spherical oxides or elongated sulfides were found to be the direct sources of cracks in the cleavage fracture within both Charpy V-notch and compact tension specimens. Cleavage cracks were found to be originated only from the steel matrix. Based on the theory of cleavage fracture and direct microscopic observations, the mechanisms were proposed for understanding the inclusion-toughness relations: (i) the oxide inclusions could indirectiy induce crack initiation by enhancing local stress concentration, therefore promoting cleavage fracture and being detrimental to the toughness; (ii) in addition to enveloping the oxides to reduce the local stress concentration, the sulfide inclusions could also break the continuous propagation of cleavage cracks in the longitudinal direction by sulfide cracking or debonding, which released the stress concentration at the crack tip and enhanced the plastic work of fracture, thereby being beneficial to the toughness improvement.
High-speed railway wheel steelPearliteCleavage fractureOxide and sulfideToughness improvement
Shi-tong Zhou、Zhao-dong Li、Lu Jiang
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National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology, Nanchang Hongkong University, Nanchang 330063, China
Department of Structural Steels, Central Iron and Steel Research Institute, Beijing 100081, China
Deakin University, Institute for Frontier Materials, Geelong, VIC 3216, Australia
NSTL
Elsevier
