Low-cycle fatigue behavior and surface treatment of a twinning-induced plasticity high-entropy alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-09, Vol.853, p.143724, Article 143724
• Main Authors: Shams, Seyed Amir Arsalan, Jang, Gyeonghyeon, Bae, Jae Wung, Amanov, Auezhan, Kim, Hyoung Seop, Lee, Taekyung, Lee, Chong Soo
• Format: Article
• Language: English
• Subjects: Alloys; Cold rolling; Crack initiation; Crack propagation; Cyclic loads; Deformation mechanisms; Deformation twin; Diameters; Elongation; Fatigue failure; Fatigue life; Fracture mechanics; Grain boundaries; Grain size; Heat treating; Heat treatment; High entropy alloys; High-entropy alloy; Low cycle fatigue; Mechanical properties; Metal fatigue; Metal plates; Nanocrystals; Strain; Surface treatment; Tensile properties; Tensile tests; Thickness; Ultrafines; Ultrasonic nanocrystal surface modification
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.143724

The low-cycle fatigue life and cyclic deformation behavior of a metastable high-entropy alloy were investigated in this study. Additionally, the effects of the ultrasonic nanocrystal surface modification (UNSM) process on tensile properties and fatigue life were evaluated. Heat treatment following the cold rolling of Fe40Mn40Co10Cr10 alloy plates resulted in the formation of a coarse grain size of 46.7 ± 19.6 μm. Additional mechanical twins were activated during tensile testing compared to the equiatomic CoCrFeMnNi alloy, leading to increased elongation. However, mechanical twins in cyclic loads appear only at high strain amplitudes. Therefore, similar to the CoCrFeMnNi alloy, the slip of dislocations was the dominant cyclic deformation mechanism and the fatigue life of the alloys were comparable. The UNSM process formed a deformed gradient layer with a thickness of approximately 200 μm on the alloy surface. In addition to mechanical twins and low-angle grain boundaries, ultrafine grains with diameters as small as 200 ± 120 nm are detectable in this layer. Although this surface treatment successfully increased the yield strength by more than 70%, fatigue crack initiation was accelerated and fatigue crack growth resistance was degraded.