Cu: Au, Cu Grain Boundary Diffusion

The grain-boundary diffusion of Au and Cu was measured in Cu bicrystals, with symmetrical near-S5, 36.9º (310)[001] coincidence-site lattice tilt grain boundaries, by using radiotracer and serial sectioning techniques. The orientations of the bicrystals were precisely determined by using the Kossel technique, and all 3 macroscopic parameters which described the orientations were evaluated. The tilt angles ranged from 33.21 to 39.26º. The grain-boundary diffusion of 195Au and 64Cu was measured as a function of the tilt angle and temperature (tables 7 to 9, figure 6). At temperatures ranging from 661 to 1030K, the orientation-dependence of each radiotracer exhibited a characteristic cusp. This was slightly below the ideal S = 5 coincidence-site lattice grain boundary. The activation enthalpy and frequency factor, as determined from lower-temperature data, exhibited a maximum slightly below the ideal S = 5 coincidence-site lattice grain boundary. These observations were considered with regard to accidental small twist and second-tilt orientations, and the corresponding dislocation networks, which were to be found in real grain boundaries. A negative deviation from a straight Arrhenius plot was observed with increasing temperature. This reflected a change in the grain boundary structure at temperatures above 800K.

Tracer Diffusion of Au and Cu in a Series of Near S = 5 (310)[001] Symmetrical Cu Tilt Grain Boundaries. E.Budke, T.Surholt, S.I.Prokofjev, L.S.Shvindlerman, C.Herzig: Acta Materialia, 1999, 47[2], 385-95

Figure 6

Diffusivity of 195Au in Σ = 5, 36.9º (310)[001] Tilt Boundaries in Cu

(Tilt angle: a - 37.74º, b - 35.88º, c - 36.53º)

Table 7

Diffusivity of 195Au in Cu along [001] Tilt Grain Boundaries

near to S = 5, 36.9º (310)[001]

Temperature (K)	Tilt Angle (º)*	sdD (m3/s)
661	33.21	3.54 x 10-21
661	35.10	5.83 x 10-21
661	35.19	8.52 x 10-21
661	35.88	7.65 x 10-21
661	36.00	6.12 x 10-21
661	36.26	2.83 x 10-21
661	36.53	1.51 x 10-21
661	36.67	9.50 x 10-21
661	37.57	1.98 x 10-20
661	37.74	2.53 x 10-20
661	38.12	1.28 x 10-20
661	39.26	7.71 x 10-21
780	33.21	2.96 x 10-20
780	35.10	4.52 x 10-20
780	35.19	4.53 x 10-20
780	35.88	5.44 x 10-20
780	36.00	3.76 x 10-20
780	36.26	2.70 x 10-20
780	36.53	1.81 x 10-20
780	36.67	5.13 x 10-20
780	36.97	6.08 x 10-20
780	37.20	6.56 x 10-20
780	37.45	7.33 x 10-20
780	37.57	6.19 x 10-20
780	37.74	8.93 x 10-20
780	38.12	6.18 x 10-20
780	39.26	5.18 x 10-20
868	35.10	7.09 x 10-20
868	35.19	8.03 x 10-20
868	36.00	8.45 x 10-20
868	36.26	8.44 x 10-20
868	37.20	8.50 x 10-20
868	37.57	1.17 x 10-19
868	39.26	9.38 x 10-20
872	33.21	8.61 x 10-20
872	33.60	7.28 x 10-20
872	35.88	1.23 x 10-19
872	36.26	1.15 x 10-19
872	36.53	7.01 x 10-20
872	36.67	1.46 x 10-19
872	38.12	1.41 x 10-19
978	33.21	1.80 x 10-19
978	35.19	1.65 x 10-19
978	35.88	1.44 x 10-19
978	36.00	2.03 x 10-19
978	36.26	1.88 x 10-19
978	36.53	1.31 x 10-19
978	36.67	2.18 x 10-19
978	37.57	2.23 x 10-19
978	37.74	2.77 x 10-19
978	38.12	2.42 x 10-19
978	39.26	1.87 x 10-19
1030	33.21	2.45 x 10-19
1030	35.10	2.37 x 10-19
1030	35.19	2.52 x 10-19
1030	35.88	2.18 x 10-19
1030	36.00	2.65 x 10-19
1030	36.26	2.40 x 10-19
1030	36.53	1.86 x 10-19
1030	36.67	3.24 x 10-19
1030	37.57	3.62 x 10-19
1030	37.74	3.42 x 10-19
1030	38.12	3.38 x 10-19
1030	39.26	2.72 x 10-19

with respect to the [001] axis

Table 8

Diffusivity of 64Cu in Cu at 919K along [001] Tilt Grain Boundaries

near to S = 5, 36.9º (310)[001]

Tilt Angle (º)	sdD (m3/s)
36.00	6.61 x 10-20
36.26	5.68 x 10-20
36.53	5.85 x 10-20
36.67	7.01 x 10-20
37.57	7.25 x 10-20

Table 9

Diffusivity Parameters for 195Au in Cu

Tilt Angle (º)	Temperature (K)	sdDo (m3/s)	E (kJ/mol)
33.21	661-872	2.1 x 10-15	72.9
35.10	661-780	3.9 x 10-15	73.8
35.19	661-780	4.9 x 10-16	60.2
35.88	661-872	9.0 x 10-16	63.9
36.00	661-868	1.3 x 10-15	67.5
36.26	661-872	6.9 x 10-15	80.3
36.53	661-872	1.2 x 10-14	87.3
36.67	661-872	7.3 x 10-16	61.9
37.57	661-1030	5.0 x 10-17	43.2
37.74	661-780	9.6 x 10-17	45.3
38.12	661-872	2.5 x 10-16	54.3
39.26	661-780	2.0 x 10-15	68.5