Decomposition and crystallization behaviour of the amorphous Ni39Pd43P18 and Ni37Pd45P18 alloys

Abstract

Dedicated t o Prof. Dr. A. SEEGER on the occasion of his 60t.h birthday The isothermal annealing of the amorphous alloys a t 677 K (above the crystallization peak K, in the DSC plot) leads to the formation of probably more than one metastable phase in the initially amorphous matrix; one of these phases is ferromagnetic a t room temperature. By annealing the amorphous alloys at 600 K (first peak in the DSC (differential-scanning-calorimetry) plot, formerly interpreted as phase separation into two amorphous phases), microcrystallites are formed in the amorphous matrix, which are proved by electron microscopy investigations. These crystallites are not ferromagnetic at room temperature.Eine isotherme Auslagerung der amorphen Legierungen bei 677 K (oberhalb des Kristallisationspeaks K, in dem DSC-Plot) fuhrt wahrscheinlich zur Bildung von mehr als einer metastabilen Phase, von denen eine bei Raumtemperatur ferromagnetisch ist. Bei der Auslagerung der amorphen Legierungen bei 600 K (erstes Maximum der DSC (differential-scanning-calorimetry)-Darstellung), bei der friiher eine Trennung in zwei amorphe Phasen angenommen wurde, bilden sich durch elektronenmikroskopische Untersuchungen nachgewiesene Mikrokristallite in der amorphen Matrix. Diese sind bei Raumtemperatur nicht ferromagnetisch.

Abnormal behavior of supercooled liquid region in bulk-forming metallic glasses

“…As a consequence, the liquid becomes a glassy solid with a different metastable equilibrium configuration that depends on thermal histories. Observations of this phenomenon have been reported for Pd-Y -Si ͑Y =Cu,Ag,Au͒, 5,6 Pd-Ni-P, [7][8][9] and Zr-Be-X ͑X =Ti,Nb͒. Thus, most studies on the glass transition behavior have been performed by measuring viscosity or by using thermal analysis during heating.…”

“…However, this glass↔ liquid transition is not a "transition" in the general thermodynamic sense, which is a kinetic event by the crossing of an experimental time scale and the time scales for atomic rearrangements. [5][6][7][8][9][10] Amorphous alloys are metastable and, thus, can decompose or phase separate into a few amorphous phases without crystallization at elevated temperatures. Due to the limitations of experimental accuracy, it is difficult to observe the glass transition behavior during cooling.…”