Crack growth behavior of low-alloy bainitic 51CrV4 steel

The crack growth behavior of low-alloy bainitic 51CrV4 steel was investigated. The current results indicate that the stress state present during the isothermal bainitic transformation has a strong influence on the crack propagation behavior in the near threshold regime, when the crack growth direction is perpendicular to the loading axis of the original sample undergoing phase transformation. However, the influence of stresses superimposed during the bainitic transformation on the crack growth behavior vanishes when the stress ratio is reduced from R=0.5 to R=0.1. Microstructural investigations revealed a locally pinned crack, indicating that the crack growth behavior in the near threshold regime is also strongly dependent on the local microstructure. Overall, the current results constitute the first step towards establishing a database for understanding and modeling the crack growth behavior in final work pieces exhibiting functionally-graded microstructures.