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 thermo-mechanical 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.