Ultrabroad distribution of multiple anelasticities in O-doped refractory multiprincipal element alloys

Oxygen interstitial solutes have traditionally been thought to occupy only octahedral interstices in body-centered cubic (bcc) metals. However, there is ongoing debate about the competition between tetrahedral and octahedral interstitial sites for oxygen solutes in multi-principal element alloys, especially following recent experimental evidence obtained using deep-sub-angstrom-resolution electron ptychography. The driving force and atomistic mechanism behind the observed preference switch remain unclear. In this study, we systematically investigate the competition between tetrahedral and octahedral sites for oxygen, nitrogen, and carbon solute atoms in bcc NbTiZr alloys using density functional theory calculations. At dilute concentrations, these small interstitial solutes are observed to preferentially reside in octahedral interstices. Notably, we demonstrate that solutes can switch from octahedral to tetrahedral sites with increasing lattice expansion, interstitial solute concentration, and spatial heterogeneity. This transition is explained by a crossover in elastic strain energy associated with solutes in the two competing interstices. Our findings provide a deeper understanding of the behavior of small interstitial solutes and their solid solution strengthening effects in bcc multi-principal element alloys.

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The Microstructural Evolution and Mechanical Properties of Boron-Doped Ti35Zr30V10Nb25 Refractory High-Entropy Alloy

Wang,

Sun,

Liu

et al. 2024

Crystals

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The addition of oxygen or nitrogen in refractory high-entropy alloys (HEAs) has been widely reported, but studies on boron-doped HEAs have mainly focused on the segregation of boron elements at grain boundaries. The changes in the microstructure and mechanical properties in TiZrNb-based HEAs remain enigmatic. In this work, boron-doped Ti35Zr30V10Nb25 (Ti35-xB) refractory HEAs were designed to elucidate their microstructural evolution and mechanical properties. Unlike oxygen and nitrogen, trace amounts of boron addition result in the formation of borides, and boron exhibits a strong repulsion towards Zr, leading to Zr-depleted borides. Borides distributed along the grain boundaries refine the grain size and dendritic structure. The borides and structural refinement effect enhance the strain-hardening capacity and uniform elongation, resulting in an over 15% uniform elongation for Ti35-0.25B.

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Ultrabroad distribution of multiple anelasticities in O-doped refractory multiprincipal element alloys

Cited by 3 publications

References 77 publications

Oxygen and nitrogen effects on anelasticity and mechanical property of Ti35Zr30V10Nb25 multi-principal element alloys

Oxygen and nitrogen effects on anelasticity and mechanical property of Ti35Zr30V10Nb25 multi-principal element alloys

Tetrahedral versus Octahedral Interstitials Sites for Oxygen Solutes in NbTiZr Medium-Entropy Alloy

The Microstructural Evolution and Mechanical Properties of Boron-Doped Ti35Zr30V10Nb25 Refractory High-Entropy Alloy

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