# The Study of Low-Cycle Fatigue Properties and Microstructure Along the Thickness Direction of a 460 MPa Marine Engineering Steel

## TL;DR

This study examines how the microstructure and fatigue life of a marine steel change across its thickness, affecting performance and durability.

## Contribution

The paper introduces a prediction model for low-cycle fatigue life based on microstructural changes and experimental data.

## Key findings

- Fatigue life decreases as grain size increases and high-angle grain boundaries decrease.
- Cyclic hardening and softening are linked to dislocation activity during fatigue tests.
- A prediction model using Basquin and Coffin–Manson relationships aligns well with experimental results.

## Abstract

This study investigated a 460 MPa marine engineering steel’s microstructure and low-cycle fatigue (LCF) behavior along the thickness direction. The results showed that the low-cycle fatigue life was reduced from 9681, 4395, 2107, 1020, 829 to 7222, 1832, 1015, 630, 242 with the specimen taken from the surface to the middle of steel plate, increasing grain size and decreasing the content of high-angle grain boundaries (HAGBs). All specimens showed notable cyclic hardening and softening. This was related to the dislocation movement, interaction, accumulation, annihilation, and dynamic recovery during fatigue tests. Furthermore, the crack propagation paths in the fatigue specimens were also observed and discussed. Finally, the Basquin and Coffin–Manson relationships were used to suggest a prediction model for the LCF life at strain amplitudes ranging from 0.4% to 1.2%, and the anticipated outcomes agreed well with the test results.