Size-dependent microstructures in rapidly solidified uranium-niobium powder particles

JOURNAL OF NUCLEAR MATERIALS

卷:479

Article

McKeown, Joseph T.¹  Hsiung, Luke L.¹  Park, Jong M.²  Ryu, Ho J.³  Turchi, Patrice E. A.¹  King, Wayne E.¹ 

[1] Lawrence Livermore Natl Lab, Div Mat Sci, Phys & Life Sci Directorate, Livermore, CA 94551 USA

[2] Korea Atom Energy Res Inst, Daejeon 305353, South Korea

[3] Korea Adv Inst Sci & Technol, Daejeon 305701, South Korea

关键词: Powder processing;    Alloys;    Rapid solidification;    Solidification microstructure;   

DOI  :  10.1016/j.jnucmat.2016.06.023

来源: Elsevier

【 摘 要 】

The microstructures of rapidly solidified U-6wt% Nb powder particles synthesized by centrifugal atomization were characterized using scanning electron microscopy and transmission electron microscopy. Observed variations in microstructure are related to particle sizes. All of the powder particles exhibited a two-zone microstructure. The formation of this two-zone microstructure is described by a transition from solidification controlled by internal heat flow and high solidification rate during recalescence (micro-segregation-free or partitionless growth) to solidification controlled by external heat flow with slower solidification rates (dendritic growth with solute redistribution). The extent of partitionless solidification increased with decreasing particle size due to larger undercoolings in smaller particles prior to solidification. The metastable phases that formed are related to variations in Nb concentration across the particles. The microstructures of the powders were heavily twinned. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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