Recent Advances in the Three-dimensional Characterization ofMartensite/Bainite Hierarchical Microstructures

Author of the article:FANG Yu1, LIU Feilong1, SHEN Ximei1, WANG Lei2, SONG Shaojie1, LIU Feng1

Author's Workplace：1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China; 2. StateKey Laboratory of Oil and Gas Equipment, CNPC Tubular Goods Research Institute, Xi'an 710077, China

Key Words：three-dimensional characterization; martensite; bainite; hierarchical microstructure; hierarchical microstructureboundary

Abstract：Lath martensite/bainite are key microstructural features that enable the synergistic optimization of strength andtoughness in high-strength steels. Their complex hierarchical microstructures play a crucial role in tailoring the mechanicalperformance. In recent years, the rapid development of three-dimensional (3D) characterization techniques has providedunprecedented opportunities for an in-depth understanding of their internal structural evolution. This review first traces thehistory of martensite/bainite research and highlights the importance of 3D characterization in revealing their crystallographicorientation features and hierarchical microstructures. Systematically summarizes the principles of mainstream 3Dcharacterization techniques and compares their advantages and limitations in terms of spatial resolution, data acquisitionefficiency, and applicable length scales. Accordingly, this review focuses on four key aspects of three-dimensionalcharacterization of martensite/bainite laths: (1) the geometric morphology of hierarchical microstructures in three dimensions;(2) the distribution characteristics of hierarchical microstructure boundary networks in three-dimensional space; (3) thenucleation, growth, and impingement behavior of bainitic laths; (4) the influence of hierarchical martensitic structures onfracture resistance. Finally, after discussing the current limitations and challenges, the review outlines promising futureresearch directions.