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

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...

Effect of microstructure induced anisotropy on fatigue behaviour of functionally graded Inconel 718 fabricated by additive manufacturing

In this paper, the effect of microstructural anisotropy on the fatigue crack growth behaviour of the functionally graded Inconel 718 fabricated through laser powder bed fusion (L-PBF) is investigated. Different manufacturing parameters, including low and high laser powers, were used to produce a variety of non-graded (NG) and functionally...

Relating matrix stress to local stress on a hard microstructural inclusion for understanding cleavage fracture in high strength steel

Macroscale cleavage fracture toughness of high strength steels is strongly related to the fracture of hard microstructural inclusions. Therefore, an accurate determination of the local stress on these inclusions based on the matrix stress is necessary for the statistical modelling of macroscale cleavage fracture. This paper presents...

A comprehensive quantitative characterisation of the multiphase microstructure of a thick-section high strength steel

The through-thickness heterogeneous microstructure of thick-section high strength steels is responsible for the significant scatter of properties along the thickness. In this study, in order to identify the critical microstructural features in the fracture behaviour and allow for design optimisation and prediction of structural failure, the...

Microstructure-informed statistical modelling of cleavage fracture in high strength steels considering through-thickness inhomogeneities

Thick section S690 QT steel is modelled with a modified multibarrier model that is based on the weakest-link mechanism. Segregation bands are modelled as discrete layers which have different grain size, yield properties, and local fracture parameters from outside of the bands. The results show that embrittlement from segregation bands can...

Cleavage fracture micromechanisms in thick-section quenched and tempered S690 high-strength steels

For structural assessment and optimal design of thick-section high-strength steels in applications under harsh service conditions, it is essential to understand the cleavage fracture micromechanisms. In this study, we assess the effects of through-thickness microstructure of an 80-mm-thick quenched and tempered S690 high-strength steel, notch...

Cleavage fracture micromechanisms in simulated heat affected zones of S690 high strength steels

High strength steels are widely used for structural applications, where a combination of excellent strength and ductile-to-brittle transition (DBT) properties are required. However, such a combination of high strength and toughness can be deteriorated in the heat affected zone (HAZ) after welding. This work aims to develop a relationship...

Microstructure-based cleavage parameters in bainitic, martensitic, and ferritic steels

Multi-barrier cleavage models consider cleavage fracture which is characterized by a series of microscale events. One of the challenges for multi-barrier cleavage models is the strong variations of cleavage parameters across different types of steels. The source and magnitude of the variations have not been studied systematically. In the...

Microstructure-based cleavage modelling to study grain size refinement and simulated heat affected zones of S690 high strength steel

Study of the cleavage behavior of heat treated S690 steel by a microstructure-based approach combined with finite element analysis is present in this paper. Cleavage simulations of steels subjected to heat treatments that cause grain refinement or simulate heat affected zones are performed, and are compared with experiments. It is found that...