Superior gradient heterostructured alloys fabricated by laser powder bed fusion via annealing and ultrasonic nanocrystal surface modification

Kim, Rae Eon; Karthik, G.M.; Amanov, Auezhan; Heo, Yoon-Uk; Jeong, Sang Guk; Gu, Gang Hee; Park, Hyojin; Kim, Eun Seong; Lee, Do Won; Kim, Hyoung Seop

doi:10.1016/j.scriptamat.2023.115422

Cited by 12 publications

(1 citation statement)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the elastic-plastic interface with a larger strength differential on both sides will generate a higher strain gradient, which needs to be accumulated by more GNDs, causing a higher increment of the GND density in the 1000-4 sample compared to the 1050-5 sample at the same strain. Accompanied by the accumulation of the GNDs, forward stress in the relatively harder layer and back stress in the relatively softer layer are produced accordingly [17,23], which collectively generate HDI strengthening and hardening [24], leading to the good strength-ductility combination for the inverse gradient-grained CoCrFeMnNi HEA [25]. To quantitively investigate the evolution of HDI strengthening and hardening during deformation, the true stress-strain curves under the loading-unloading-reloading tensile tests of the experimental CoCrFeMnNi HEAs with inverse gradient-grained structures are presented in Figure 7a.…”

Section: Microstructural Evolution During Tensile Deformationmentioning

confidence: 99%

Strength–Ductility Mechanism of CoCrFeMnNi High-Entropy Alloys with Inverse Gradient-Grained Structures

Chen,

Hu,

Wang

et al. 2024

Materials

View full text Add to dashboard Cite

The microstructures and mechanical properties of equiatomic CoCrFeMnNi high-entropy alloys (HEAs) treated with various processing parameters of laser surface heat treatment are studied in this paper. The typical inverse gradient-grained structure, which is composed of a hard central layer and a soft surface layer, can be obtained by laser surface heat treatment. A much narrower gradient layer leads to the highest yield strength by sacrificing ductility when the surface temperature of the laser-irradiated region remains at ~850 °C, whereas the fully recrystallized microstructure, which exists from the top surface layer to the ~1.05 mm depth layer, increases the ductility but decreases the yield strength as the maximum heating temperature rises to ~1050 °C. Significantly, the superior strength–ductility combination can be acquired by controlling the surface temperature of a laser-irradiated surface at ~1000 °C with a scanning speed of ~4 mm/s due to the effect of hetero-deformation-induced strengthening and hardening, as well as the enhanced interaction between dislocation and nanotwins by the hierarchical nanotwins. Therefore, retaining the partial recrystallized microstructure with a relatively high microhardness in the central layer, promoting the generation of hierarchical nanotwins, and increasing the volume proportion of gradient layer can effectively facilitate the inverse gradient-grained CoCrFeMnNi HEAs to exhibit a desirable strength–ductility synergy.

show abstract