Features of Phase Formation Processes in Amorphous Alloys …
411
G
α−i
(c 2 ) = G
α
(c 2 ) − G
i
(c 2 ),
G
α−α
(c 2 ) = G
α
(c 2 ) − G
α
(c 20 ),
(2)
where G
α
(c 2 ) and G
i
(c 2 )—concentration dependences of the relative integral
Gibbs free energy in the amorphous (α) and crystalline (i) phases; c 20 —initial
concentration of the second component in the α-phase; c 2 —arbitrary concentration
of the second component in the α- and i-phases, σ —surface tension at the boundary
of two phases, V —molar volume, N —number of atoms per unit volume; a—atomic
diameter, D—diffusion coefficient.
Taking into account that during crystallization in the binary system several stable
formations are formed, as well as the possible occurrence of metastable phases, (2)
is generalized to the
J i =
1
0
J
i (c 2 )dc 2 , ,
(3)
where i = β, γ, δ, ε-phases.
The total frequency of nucleation J of different types will be written in the form
J =
k
i=1
J i ,
(4)
where k—the number of stable and metastable phases occurring during crystallization.
The linear growth rate of crystals in the case of binary alloys is described by the
equation
U i =
D
a
1 − exp
−
G
α−i
−
G
α−α
RT
.
(5)
Equation (1) is solved by methods of numerical integration, from which all values
are determined X i (t) for the system; X (t) =
k
i=1 X i .
Let us consider the possibilities and thermodynamic preconditions of the phase
stratification process in amorphous binary alloys. As in the case of liquid systems,
the possibility of stratification in amorphous alloys is associated with the behavior
of the concentration dependence of the relative integral free Gibbs energy. For most
binary amorphous alloys there is a concentration region in which the free energy of
a mixture of two amorphous phases is less than that of one amorphous phase. In this
concentration region, for some amorphous metal alloys, there is a phase stratification,
which occurs by the type of spinodal decay without the origin of crystals. This
process is a special case of the initial stage of phase transformation when the system
411
G
α−i
(c 2 ) = G
α
(c 2 ) − G
i
(c 2 ),
G
α−α
(c 2 ) = G
α
(c 2 ) − G
α
(c 20 ),
(2)
where G
α
(c 2 ) and G
i
(c 2 )—concentration dependences of the relative integral
Gibbs free energy in the amorphous (α) and crystalline (i) phases; c 20 —initial
concentration of the second component in the α-phase; c 2 —arbitrary concentration
of the second component in the α- and i-phases, σ —surface tension at the boundary
of two phases, V —molar volume, N —number of atoms per unit volume; a—atomic
diameter, D—diffusion coefficient.
Taking into account that during crystallization in the binary system several stable
formations are formed, as well as the possible occurrence of metastable phases, (2)
is generalized to the
J i =
1
0
J
i (c 2 )dc 2 , ,
(3)
where i = β, γ, δ, ε-phases.
The total frequency of nucleation J of different types will be written in the form
J =
k
i=1
J i ,
(4)
where k—the number of stable and metastable phases occurring during crystallization.
The linear growth rate of crystals in the case of binary alloys is described by the
equation
U i =
D
a
1 − exp
−
G
α−i
−
G
α−α
RT
.
(5)
Equation (1) is solved by methods of numerical integration, from which all values
are determined X i (t) for the system; X (t) =
k
i=1 X i .
Let us consider the possibilities and thermodynamic preconditions of the phase
stratification process in amorphous binary alloys. As in the case of liquid systems,
the possibility of stratification in amorphous alloys is associated with the behavior
of the concentration dependence of the relative integral free Gibbs energy. For most
binary amorphous alloys there is a concentration region in which the free energy of
a mixture of two amorphous phases is less than that of one amorphous phase. In this
concentration region, for some amorphous metal alloys, there is a phase stratification,
which occurs by the type of spinodal decay without the origin of crystals. This
process is a special case of the initial stage of phase transformation when the system