title: Strength gradient enhances fatigue resistance of steels.
abstract: Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch's tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility.
authors.affiliation: LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, P.R. China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Faculty of Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Jiabin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Laboratory for Microstructures, Shanghai University, Shanghai 200444, P.R. China.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.affiliation: Faculty of Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Wang
authors.affiliation: LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, P.R. China.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Wei
authors.affiliation: School of Engineering, Brown University, Providence, RI 02912, USA.
authors.forename: Huajian
authors.initials: H
authors.lastname: Gao