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Discovery of Ni activated sintering of MoNbTaW predicted by a computed grain boundary diagram

delete2024-01-01
delete6
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OA
AI
S
Sashank Shivakumar
K
Keqi Song
C
Chunyang Wang
T
Tianjiao Lei
H
Huolin L. Xin
T
Timothy J. Rupert
J
Jian Luo *
DOI:10.1016/j.scriptamat.2023.115777delete
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Abstract

Abstract

En 中文
Activated sintering of refractory metals represents a classical phenomenon in powder metallurgy. This study discovers that Ni addition can enhance sintering of MoNbTaW both above and below the bulk solidus compo-sition at 1800 degrees C, thereby demonstrating the first example of activated sintering of a high-entropy alloy. To probe the underlying mechanism, experiments reveal complete grain boundary (GB) wetting above the bulk solidus composition, which logically infers the stabilization of a liquid-like interfacial phase (GB complexion) in a prewetting region below the bulk solidus composition. Furthermore, bulk CALPHAD (calculation of phase dia-gram) methods have been extended to model GBs in Ni-doped MoNbTaW to compute a GB phase diagram to forecast high-temperature GB disordering in the prewetting region and rationalize the observed Ni-activated sintering of MoNbTaW. Only weak GB segregation of Ni is found in furnace-cooled specimens, which suggests GB drying during cooling, consistent with the observed nanoscale precipitates along GBs.
Keywords:
Activated sintering
Grain boundary
High-entropy alloys
Refractory alloys
Prewetting
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Journal

Scripta Materialia cover
Scripta Materialia
IF:
5.6
Papers:
1.6W
Citations:
5.1W

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University of California System cover
University of California System
Scholars:
37.2W
Papers: 33.6W
Citations: 6.6K
U
University of California San Diego
Scholars:
4.6W
Papers: 3.5W
Citations: 924
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