Cleavage Fracture Micromechanisms of High Strength Steel and its Heat-Affected Zones

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The use of materials in increasingly severe service conditions raises concerns about structural safety with respect to cleavage fracture. There are three main material-related challenges that structures face under harsh environments: 1) the trade-off between strength and toughness; 2) the ductile-to-brittle transition behaviour of BCC high strength steels; 3) the inhomogeneous microstructures found in multiphase steels, thick-section steels, and welded structures. Therefore, the objective of this research is to systematically investigate the cleavage fracture micromechanisms in high strength steels considering diverse microstructures (e.g., as-received commercial steel, thermally simulated heat-affected zones, and grain refined microstructure) and experimental conditions (e.g., plastic constraint and temperature). Thereby, this study provides a thorough understanding of the effect of the microstructural details on cleavage fracture behaviour of high strength steel structures allowing for failure control and improvement of cleavage-resistant steel’s design...