Effects of ultrasonic surface rolling process on microstructure and mechanical properties of metastable Fe50Mn30Co10Cr10 high-entropy alloy fabricated by laser directed energy deposition
Yaoyao Wang, Fangyi Li, Yanle Li, Jianfeng Li, Heng Chen, Yunjian Bai
Abstract
Although laser directed energy deposition (LDED) technology had significant advantages in the integrated manufacturing and rapid repair of complex large components, its forming process was prone to defects and the formation of columnar grains, which subsequently affected the overall performance of the components. To address these challenges, this study introduced the ultrasonic surface rolling process (USRP) as a post-treatment method to modify the surface of Fe 50 Mn 30 Co 10 Cr 10 high-entropy alloy (HEA) fabricated by LDED under different loads. Multiscale characterization results revealed that USRP treatment induced multilevel gradient structures near the material's surface, characterized by gradient distributions in various structural features, including dislocation density, the HCP phase, and grain size distribution. Under a USRP load of 500 N, the sample exhibited superior strength-ductility synergy, with a surface hardness of 386 HV. The yield strength and ultimate tensile strength increased by approximately 27.2 % and 11.1 %, respectively. The strength enhancement was attributed to dislocation strengthening, densification strengthening, Hall-Petch strengthening, and intrinsic strengthening. Additionally, the synergistic effects of hetero-deformation induced (HDI) hardening, transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) contributed to the excellent work hardening capability and ductility of the sample.