Transient Liquid Phase Bonding in the Ni-P system
Finite Element Approximation using COMSOL
Effective Reciprocal Activity Coefficient Formulation
1.- Convert all concentrations from atomic percent to mass fraction and call
it C
2.- Introduce the activity of phosporus c
3.- Relate the activity of phosporus c to the phosporus concentration C .
From thermodynamics
C = gamma c or c = (1/gamma) C = b C
where b is the reciprocal activity coefficient. For ideal solutions b=1.
4.- Assume the fully solid and fully liquid phases are ideal (b=1). However,
in the concentration range between 0.1 and 17 a/o
(i.e. 0.009 to 0.11 in mass fraction units), where the liquid and soilid phases
coexist, the activity c has constant value = 0.01 (chemical equilibrium
condition). To account for this, introduce the effective
reciprocal activity coefficient beff as
beff = (0.11 - 0.009)/(0.011-0.009) = 50.5
where the range of activity 0.009 - 0.011 is centered in 0.01