Microstructure refinement and bicontinuity formation by distributed internal melting at the Ni₃Sn₄ peritectic

Guided by a current interest in processing schemes, such as liquid-metal dealloying, providing fine-scale bicontinuous metal microstructures, we investigate the microstructure evolution during the peritectic melting of Ni₃Sn₄. The product microstructure is an interconnected array of spherical clusters of crystallographically aligned Ni₃Sn₂ ligaments, interpenetrated by a contiguous liquid phase. When quenched to room temperature, the prevalent microstructure consists of two interpenetrating solid phases. Leaching the solidified Sn melt produces monolithic porous bodies of Ni₃Sn₂. The characteristic structure size can reach down to 2 μm, a microstructure refinement by almost 2 orders of magnitude as compared to the 150 μm grain size of the master alloy. Remarkably, a more severe refinement is achieved at higher annealing temperatures. Our experiments identify liquid-film migration as the controlling process, here concurrent with constitutional supercooling and cellular solidification. We argue that peritectic melting exemplifies a more general family of processes of distributed internal melting (DIM). These processes exploit the abundant nucleation of regions of melt, finely distributed throughout a parent microstructure, when the alloy is heated into a two-phase solid–liquid regime of its phase diagram. DIM provides a novel and versatile pathway to fine-scale bicontinuous microstructures.

Subjects

Constitutional supercooling

Liquid film migration

Liquid-metal dealloying

NiSn alloy

Peritectic melting

DDC Class

620.11: Engineering Materials

Lizenz

https://creativecommons.org/licenses/by/4.0/

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publishedVersion

Name

1-s2.0-S2238785426004394-main.pdf

Type

Main Article

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5.04 MB

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Microstructure refinement and bicontinuity formation by distributed internal melting at the Ni₃Sn₄ peritectic