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Microstructure and Fracture Toughness of Cast and Forged Ultra-High-Strength, Low-Alloy (UHSLA) Steels

J. Zeman,Stanislav Rolc,J. Buchar,Jaroslav Pokluda-1990-01-01
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TL;DRAbstract

This paper describes the fracture toughness and microstructure relations for ultra-high-strength, low-alloy (UHSLA) steels corresponding to AISI 4340 composition. The steels were either cast or forged, heat treated at austenitizing temperatures from 840 to 1100°C, oil quenched and tempered at 180 and 650°C. Fracture toughness, tensile, and Charpy impact toughness tests, and testing of apparent fracture toughness under the influence of notch root radius, were performed simultaneously. Investigation of microstructures and corresponding mechanical properties, as well as fractographic examinations and evaluation of chemical heterogeneity, made it possible to elucidate the alteration of fracture behavior. It was found that cast low-tempered steel has higher fracture toughness (KIc) than forged steels, though its conventional mechanical properties are lower. Increasing KIc caused by the higher austenitizing temperature of forged steel was also observed. The coarsened prior austenite grains a

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This paper describes the fracture toughness and microstructure relations for ultra-high-strength, low-alloy (UHSLA) steels corresponding to AISI 4340 composition. The steels were either cast or forged, heat treated at austenitizing temperatures from 840 to 1100°C, oil quenched and tempered at 180 and 650°C. Fracture toughness, tensile, and Charpy impact toughness tests, and testing of apparent fracture toughness under the influence of notch root radius, were performed simultaneously. Investigation of microstructures and corresponding mechanical properties, as well as fractographic examinations and evaluation of chemical heterogeneity, made it possible to elucidate the alteration of fracture behavior. It was found that cast low-tempered steel has higher fracture toughness (KIc) than forged steels, though its conventional mechanical properties are lower. Increasing KIc caused by the higher austenitizing temperature of forged steel was also observed. The coarsened prior austenite grains a

Keywords

Materials scienceCharpy impact testFracture toughnessMicrostructureAusteniteMetallurgyGrain boundaryToughness

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