Analysis of hydrogen trapping behaviour in plastically deformed quenching and partitioning steel in relation to microstructure evolution by phase transformation

The relationship between plastic deformation and hydrogen transport behaviour in the quenching and partitioning (Q&P) steel is studied. The evolution of microstructure after different levels of plastic de-formation is characterized using the electron backscatter diffraction (EBSD) and X-ray diffraction technique. Also, the hydrogen diffusion and trapping of the plastically deformed Q&P steel are investigated using the hydrogen permeation electrochemical method and thermal desorption spectroscopy (TDS) on pre-strained specimens up to 14% engineering strain. The major findings through the experimental approach can be summarized as follows: (1) retained austenite fraction in Q&P steel decreased after plastic deformation; (2) the geometrically necessary dislocation (GND) density measured by KAM analysis increased; (3) hydrogen diffusivity decreased, while solubility increased as the plastic deformation increased. The increase in hy-drogen trapping in the Q&P steel with plastic deformation can be attributed to the enhanced hydrogen trapping environment by increased dislocation density in ferrite and martensite transformed from me-tastable austenitic phase. The TDS analysis could support the hydrogen-trapping characteristics of Q&P steel, in which two major peaks were measured in different temperature ranges. Moreover, the EBSD ob-servation and scanning transmission electron microscope (STEM) using transmission Kikuchi diffraction (TKD) analysis provided good correlation with the result of TDS analysis.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The relationship between plastic deformation and hydrogen transport behavior in quenching and partitioning (Q&P) steel was investigated. The evolution of microstructure and hydrogen diffusion and trapping characteristics were characterized using experimental methods. The major findings include the decrease in retained austenite fraction, the increase in geometrically necessary dislocation density, the decrease in hydrogen diffusivity, and the increase in solubility with increasing plastic deformation. The enhanced hydrogen trapping in the Q&P steel with plastic deformation was attributed to the increased dislocation density in ferrite and martensite. Experimental analysis using thermal desorption spectroscopy (TDS), electron backscatter diffraction (EBSD), and scanning transmission electron microscope (STEM) provided supporting evidence for hydrogen trapping characteristics and microstructure correlation.