Nanocomposites and nanomaterials

Effect of pressure treatment on the process of cleaning the amorphous phase from frozen-in crystallisation centers

V.I. Lysov1, T.L. Tsaregradskaya1, G.V. Saenko1 , O.V. Turkov1, 

1 Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Street, 
City of Kyiv, 01601 Ukraine

Numerous researches confirm that at got amorphous state by the rapidly quenched from liquid phase, the frozen-in crystallizations centers are presents. Consider function , that determines  the difference of chemical potentials in amorphous - and crystalline-phases, at deviation of the system from the state of thermodynamics equilibrium [1]:
,
where;  are the chemical potentials undeformed amorphous - and crystalline -phases accordingly,  is the  pressure in -phase on the border with crystalline centers (-phase);  is  the  pressure in -phase,  are the molar volume - and -phases accordingly.  Thus, through external influences, for example creations of additional pressure, it is possible to influence on a function , and at  , to create conditions, at that the frozen-in crystallization centers dissolve and thus, thermal stability of amorphous alloys rises. By means of high sensitive dilatometric method research of influence  pressure treatment on the temperature of beginning of intensive crystallization  of amorphous alloys based оn Fe, Ni, Co were executed. The temperature beginning intensive crystallization for amorphous alloys after pressure treatment increased on (20-40) К. Thus there is dissolution frozen-in crystallization centers present in the original sample that confirmed by results of electronmicroscopic researches.These results can be explained by that over the pressure treatment of amorphous alloys brings to substantial displacement of phase equilibrium in the heterogeneous system: amorphous matrix – frozen-in crystallization centers. Thus, it is experimentally confirmed that external influences that result in reduction of difference of chemical potentials of і component in amorphous matrix and frozen-in crystallization center result in dissolution of the frozen-in crystallization сenters.
 
1. Shpak A.P., Lysov V.I., Kunitsky Yu.A., Tsaregradskaya T.L. Crystallisation and amorphysation of metallic systems.– Kyiv: Akadempriodika, 2002.–208 p. (in Ukrainian).