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Analysis of phase stability and chemical segregation in the Mo-V alloys using a generalized embedded atom method potential

A new interatomic potential for the Mo-V system is introduced to facilitate the study of phase stability and mechanical properties at lower temperatures. This potential is based on a generalization of the embedded atom method and includes contributions from embedding energy, explicit two- and three-body interactions and nonlocal many-body interaction terms. The parameters of the potential are optimized by using data from ab initio density functional theory (DFT) calculations. The potential is rigorously validated across a range of physical properties, such as elastic constants, equation of states, phonon dispersion curves, point defect properties and melting temperatures for different compositions. Even though our potential is trained on a small dataset, its accuracy is comparable to available machine learning potentials for Mo and V. Furthermore, our results show that an ordered B2 phase is stable at low temperatures in alloys containing 50% V, but the solid solution phase is stable above 800 K. However, such long-range ordering is not observed in V-rich or Mo-rich alloys. In addition, our results show that V segregates to dislocation cores and grain boundaries.

36 MATERIALS SCIENCE↗

Analysis of correlations between intrinsic ductility and electronic density of states in refractory alloys

High entropy alloys (HEAs) correspond to a new and emerging class of materials that allows us to explore a large composition space to tune mechanical strength and thermal stability. Therefore, to design better alloys, it is important to scan the high-dimensional space of chemistry, composition and temperature. Here, to facilitate this search, we present a method to screen intrinsically ductile body centered cubic (BCC) refractory alloys from electronic structure calculations by using the density of states (DOS) at the Fermi level, g(μ F ). This correlation between intrinsic ductility and g(μ F ) is tested by analyzing group V (V, Nb, Ta) and VI (Mo, W) refractory metals, binary alloys, such as W-Nb, W-V, Mo-Nb and Mo-V, and refractory alloys for which experimental stress-strain measurements are available. In addition, we perform a high-throughput exploration of the entire composition space of a recently proposed alloy system, CrMoNbV, and identify compositions that exhibit high intrinsic ductility.

36 MATERIALS SCIENCE↗

Materials Data on VMo by Materials Project

MoV crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. V is bonded to six equivalent V and six equivalent Mo atoms to form VV6Mo6 cuboctahedra that share corners with eighteen equivalent VV6Mo6 cuboctahedra, edges with six equivalent VV6Mo6 cuboctahedra, edges with twelve equivalent MoV6Mo6 cuboctahedra, faces with eight equivalent VV6Mo6 cuboctahedra, and faces with twelve equivalent MoV6Mo6 cuboctahedra. All V–V bond lengths are 2.70 Å. All V–Mo bond lengths are 2.86 Å. Mo is bonded to six equivalent V and six equivalent Mo atoms to form MoV6Mo6 cuboctahedra that share corners with eighteen equivalent MoV6Mo6 cuboctahedra, edges with six equivalent MoV6Mo6 cuboctahedra, edges with twelve equivalent VV6Mo6 cuboctahedra, faces with eight equivalent MoV6Mo6 cuboctahedra, and faces with twelve equivalent VV6Mo6 cuboctahedra. All Mo–Mo bond lengths are 2.70 Å.

36 MATERIALS SCIENCE↗