About this Abstract |
| Meeting |
MS&T26: Materials Science & Technology
|
| Symposium
|
Advances in Refractory High Entropy Alloys and Ceramics
|
| Presentation Title |
Dominant Role of Second Nearest-Neighbor Bonding in Strength-Ductility Tradeoff of bcc Refractory High Entropy Alloys |
| Author(s) |
Dharmendra Pant, Suyash Varshney, Dilpuneet S. Aidhy |
| On-Site Speaker (Planned) |
Dilpuneet S. Aidhy |
| Abstract Scope |
Balancing strength and ductility in BCC refractory high entropy alloys (RHEAs) remains a fundamental challenge due to the intrinsic trade-off between bond strength and dislocation mobility. Using (DFT) calculations, we show that there is a noticeable decrease in the density of states at the Fermi level, N(Ef), within a short window of valence electron concentration (VEC) around 5.1 marking a crossover from metallic to covalent-type bonding in refractory bcc alloys. This change is driven by a disproportionate suppression of eg states, responsible for σ-type bonds along second nearest neighbor (2NN) directions, relative to t2g states. The resulting increase in 2NN stiffness outpaces the increase in the first nearest neighbor (1NN) stiffness and drives steep rise in Young’s and shear moduli, while simultaneously reducing local lattice distortion and ductility. Enrichment with higher-VEC Group VI elements amplifies these effects, whereas addition of lower-VEC Group IV and V elements reduces them. |