Fractographic observations of cleavage fracture initiation in a bainitic A508 steel

Effect of Bimodal Grain Size Distribution on Scatter in Toughness

“…Charpy tests often generate complex fracture surfaces that make it difficult to identify the original cleavage-initiation site. [29] Hence, there is a need to investigate semi-idealized microstructures and test conditions. To investigate the microstructure-toughness relation, slow blunt-notch (toughness) tests at low temperature are more ideal; such tests have been widely used for this purpose.…”

Investigation of cleavage fracture initiation in notched specimens of a C–Mn steel with carbides and inclusions

“…In previous studies, it has been found that the cleavage initiation particles are carbides [3][4][5][6][7][8][9] or inclusions [17][18][19][20][21][22][23][24][25][26][27][28][29][30] in various steels and weld metals. In present study, for the FC and CC steels in which carbides with different sizes coexist with inclusions, two types of cleavage initiation site (IC and SIC) are found in notched specimens tested at −196 and −130 • C. The IC initiation sites are related to approximately spherical small inclusions (Fig.…”

“…Thus the probability sampling the larger carbides and inclusions as potential cleavage initiators in the active zone increases. Because the interfacial strength between inclusion and matrix for the most inclusions in carbon steels is low [27,36,37], an inclusion may first debond from matrix during loading process and an interfacial crack is formed. If the interfacial crack size is large enough, and the crack plane is oriented as normal as possible to the maximum principal stress to cause sufficient stress concentration in the neighboring grain, and the included angle between the crack plane and the neighboring cleavage planes is as small as possible, the interfacial crack could propagate into neighboring ferrite grain under the combined action of the dislocation pile-up and applied stress, and a ferrite grain-sized crack is produced [38].…”

“…On the other hand, examples of inclusion-initiated cleavage fracture have also been found in weld metal [17][18][19] and various steels [20][21][22][23][24][25][26][27]. In some recent studies, TiN inclusion-induced cleavage in steels has also been reported [11,[28][29][30].…”

Effects of Inclusion Particles on the Microstructure and Mechanical Properties of High Strength Austempered Ductile Iron

“…However, inclusion particles were thought by many researchers to be detrimental to mechanical properties of steels, because they acted as the sites for forming micro-voids resulting in cleavage cracks in the process of tensile, cyclic loading or impact testing. 3,6,7) Despite the controversy, the above studies acknowledged the correlations of inclusion particles and the microstructures in commercial steels. In fact, the mechanical properties of ADI are also affected by its matrix microstructure.…”