Concentration distribution curves (c-x curves) for interdiffusion in complete solid solution of copper-nickel and iron-nickel binary alloy systems were obtained by the following three methods: (1) Experiment by using EPMA, (2) analytical computation based on a concentration independent interdiffusion coefficient (\ ilde
DConst.) and (3) approximate computation based on a concentration dependent interdiffusion coefficient (\ ilde
D(
c)) by the use of the finite element method.
The experimentally determined c-x curves were compared with two types of computed ones. Then the usefulness of a method of determining the degree of homogenization (interdiffusion or sintering) was discussed. The results were as follows:
(1) The computed c-x curve on the assumption of \ ilde
D(
c) was consistent with the experimentally obtained one, but the c-x curve on the assumption of \ ilde
DConst. was not exactly consistent with the experimentally obtained one, especially at the points d
c⁄d
x=0 and d
2c⁄d
x2=0 on the c-x curves, corresponding to the center of a foil composing the diffusion couple and the vicinity of joined interface, respectively.
(2) The degree of homogenization (interdiffusion),
H, computed on the assumption of \ ilde
D(
c) agreed with the graphically obtained value, but that on the assumption of \ ilde
DConst. deviated slightly from the graphically obtained valus.
By the use of experimental data on \ ilde
DConst. in an alloy system,
H value at any time can be estimated roughly. To obtain the exact
H value, \ ilde
D(
c) should be taken into consideration in computation.
View full abstract