TY - JOUR

T1 - Monotropic polymorphism in a glass-forming metallic alloy

AU - Pogatscher, Stefan

AU - Leutenegger, D.

AU - Schawe, J. E.K.

AU - Maris, P.

AU - Schäublin, R.

AU - Uggowitzer, Peter J.

AU - Löffler, Jörg F.

PY - 2018/5/18

Y1 - 2018/5/18

N2 - This study investigates the crystallization and phase transition behavior of the amorphous metallic alloy Au70Cu5.5Ag7.5Si17. This alloy has been recently shown to exhibit a transition of a metastable to a more stable crystalline state, occurring via metastable melting under strong non-equilibrium conditions. Such behavior had so far not been observed in other metallic alloys. In this investigation fast differential scanning calorimetry (FDSC) is used to explore crystallization and the solid-liquid-solid transition upon linear heating and during isothermal annealing, as a function of the conditions under which the metastable phase is formed. It is shown that the occurrence of the solid-liquid-solid transformation in FDSC depends on the initial conditions; this is explained by a history-dependent nucleation of the stable crystalline phase. The microstructure was investigated by scanning and transmission electron microscopy and x-ray diffraction. Chemical mapping was performed by energy dispersive x-ray spectrometry. The relationship between the microstructure and the phase transitions observed in FSDC is discussed with respect to the possible kinetic paths of the solid-liquid-solid transition, which is a typical phenomenon in monotropic polymorphism.

AB - This study investigates the crystallization and phase transition behavior of the amorphous metallic alloy Au70Cu5.5Ag7.5Si17. This alloy has been recently shown to exhibit a transition of a metastable to a more stable crystalline state, occurring via metastable melting under strong non-equilibrium conditions. Such behavior had so far not been observed in other metallic alloys. In this investigation fast differential scanning calorimetry (FDSC) is used to explore crystallization and the solid-liquid-solid transition upon linear heating and during isothermal annealing, as a function of the conditions under which the metastable phase is formed. It is shown that the occurrence of the solid-liquid-solid transformation in FDSC depends on the initial conditions; this is explained by a history-dependent nucleation of the stable crystalline phase. The microstructure was investigated by scanning and transmission electron microscopy and x-ray diffraction. Chemical mapping was performed by energy dispersive x-ray spectrometry. The relationship between the microstructure and the phase transitions observed in FSDC is discussed with respect to the possible kinetic paths of the solid-liquid-solid transition, which is a typical phenomenon in monotropic polymorphism.

KW - amorphous

KW - metals

KW - phase transformation

KW - polymorphism

UR - http://www.scopus.com/inward/record.url?scp=85047966329&partnerID=8YFLogxK

U2 - 10.1088/1361-648X/aac054

DO - 10.1088/1361-648X/aac054

M3 - Article

AN - SCOPUS:85047966329

VL - 30.2018

JO - Journal of Physics Condensed Matter

JF - Journal of Physics Condensed Matter

SN - 0953-8984

IS - 23

M1 - 234002

ER -