Plastic damage evolution in structural steel and its non-destructive evaluation

This paper reports the plastic damage evolution in low carbon structural steel and its NDT evaluation. The SEM observations reveal that the voids initiation, growth, coalescence, micro-crack propagation, and macro-crack formation are the main failure forms. The EBSD results show that with the increasing plastic strain, the KAM and ρGND within grains in LC steel increased continuously. Meanwhile, the BS value and the IPF maps quality decreased significantly. Besides, the TEM observations show that the plastic strain induced dislocation density increase and inhomogeneous dislocation distribution in LC steel, the dislocation nets structures were developed at the later plastic stages, which consist of high-density dislocation tangles. Also, the magnetic hysteresis-loop changed distinctly after the plastic strain, and the Coercivity is sensitive to the change of dislocation structure/density. Therefore, the electromagnetic technique can be utilized to assess the plastic damage in LC steel.