Short-range ordering heredity in eutectic high entropy alloys: A new model based on pseudo-ternary eutectics

Short-range ordering heredity in eutectic high entropy alloys: A new model based on pseudo-ternary eutectics

Acta Materialia

10.1016/j.actamat.2022.118512

http://dx.doi.org/10.1016/j.actamat.2022.118512

Kewu Bai, Chee Koon Ng, Ming Lin, Fengxia Wei, Shuang Li, Siew Lang Teo, Dennis Cheng Cheh Tan, Pei Wang, Delvin Wuu, Jing Jun Lee, Yong-Wei Zhang

Electronic, Optical and Magnetic Materials, Polymers and Plastics, Metals and Alloys, Ceramics and Composites

12 November 2022

Bai, K., Ng, C. K., Lin, M., Wei, F., Li, S., Teo, S. L., Tan, D. C. C., Wang, P., Wuu, D., Lee, J. J., & Zhang, Y.-W. (2023). Short-range ordering heredity in eutectic high entropy alloys: A new model based on pseudo-ternary eutectics. Acta Materialia, 243, 118512. https://doi.org/10.1016/j.actamat.2022.118512

Eutectic high entropy alloys (EHEAs) have garnered wide attention in the metal community due to their excellent castability and unique microstructures. However, the formation mechanisms of these eutectic microstructures and their compositional design remain puzzling. In this paper, we have developed a sim- ple yet unified pseudo-ternary model to unravel the puzzle of multiple eutectics in Ni-Al-containing high entropy alloys (HEAs) deploying a combination of the chemical similarity/dissimilarity coefficient con- cept, CALPHAD technique and first principle molecular dynamics simulation. Using the chemical similar- ity/dissimilarity parameters derived from CALPHAD model parameters and the eutectic valleys of Ni-Al-Cr, we reproduce the multiple eutectic patterns in the Ni-Al-containing HEAs and present a general approach for pinpointing the composition of eutectic HEA (EHEA) in the vast temperature-composition space. Aided by the first principle molecular dynamics calculation, we have shown that although the eutectic struc- tures of Ni-Al containing EHEAs are different, the formation mechanism of the eutectic structure is simi- lar, which stems from the short-range-ordering (SRO) heredity of EHEA liquid from the eutectic valleys of the pseudo Ni-Al-Cr ternary. Two EHEAs, EHEA 1 (Al 16.95 Cr 16.95 Fe 19.1 Ni 47 ) with L1 2 + B2 eutectic structures and EHEA 2 (Al 33.5 Cr 33 Co 4 Ni 29.5 ) with BCC + B2 eutectic structures were designed using the model and experimentally verified. This unified Ni-Al-Cr ternary model, validated by experimental data in both liter- ature and our fabricated EHEAs, presents a compelling solution to the long-debated grouping strategy in EHEA design and offers a new paradigm to map the complicated but intriguing eutectic microstructures in EHEAs and conventional alloys.

Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

This research / project is supported by the A*STAR - Accelerated Materials Development for Manufacturing Programme
Grant Reference no. : A1898b0043

This research / project is supported by the A*STAR - A*STAR SERC CRF Award
Grant Reference no. : NA

https://oar.a-star.edu.sg/communities-collections/articles/19246

1359-6454

Institute of Materials Research and Engineering