Effect of grain ultra-refinement on microstructure, tensile property, and corrosion behavior of low alloy steel

This work investigated the effect of grain ultra-refinement on the microstructure, mechanical property, and corrosion behavior of low alloy steels. The ultrafine-grain steels were obtained by using advanced thermomechanical processes (ATP), and their microstructures, mechanical property, and corrosion behavior were characterized by electron backscattered diffraction (EBSD), scanning electron microscopy (SEM) electrochemical measurements, and X-ray photoelectron spectrometer (XPS). The morphology of the fracture surface and the microstructures of the failed tensile specimen were analyzed to investigate the failure mechanism. Grain refinement results in a significant increase in the grain boundary density, which leads to the enhanced strength and brittle fracture. The study found that the grain boundaries have a higher pitting susceptibility and crystallographic pitting has a susceptibility in order of {111} > {101} > {001}. Ultrafine grain with a high fraction of low angle grain boundaries (LAGBs) impedes pitting corrosion.