T.O. 33B-1-1
4-8
Table 4-3. Conductivity’s of Some Commonly Used Engineering Materials.
Material
Conductivity Megaohms/Inch**
Conductivity
(%IACS)
Temperature
(°F)
Aluminum Base*
1060-0
2014-T6
2024-T3
2024-T851
5052-0
6061-T6
7075-T6
0.913
0.589
0.174
0.589
0.516
0.589
0.442
62.0
35.5 - 41.5
28.5 - 32.5
36.0 - 42.5
33.6 - 37.6
40.0 - 48.0
30.5 - 36.0
69
68
68
—
68
68
68
Copper Base
99.9%, Annealed
Cartridge Brass,
Annealed
Aluminum Bronze - 5%,
Annealed
Phosphor Bronze - 5%,
Annealed
1.473
0.412
0.250
0.221
100.0
28.0
17.0
15.0
68
68
68
68
Magnesium Base
Pure, Annealed
K60A-0
AZ31B-T5
0.560
0.442
0.273
38.0
30.0
18.5
68
68
70
Nickel Base
A, 99.4%
Monel 400
Inconel 600
0.265
0.053
0.025
18.0
3.6
1.7
68
68
70
Stainless Steel
304
430
0.353
0.423
2.4
2.9
70
70
Titanium Base
Ti-55A
6Al-4V
8A1-1Mo-1V
0.045
0.015
0.013
3.1
1.0
0.87
—
—
—
4.2.2.1.1.5 Effect of Conductivity on Eddy Currents.
The distribution and intensity of eddy currents in non-ferromagnetic materials is strongly affected by electrical
conductivity. In a material of relatively high conductivity, strong eddy currents are generated at the surface. In turn,
the strong eddy currents form a strong secondary electromagnetic field opposing the applied primary field. As a result
the strength of the primary field decreases rapidly with increasing depth below the surface. In poorly conductive
materials, the primary field generates small amounts of eddy currents, which produce a small opposing secondary field.
Therefore, in highly conductive materials, strong eddy currents are formed near the surface, but their strength reduces
rapidly with depth. In poorly conductive materials, weaker eddy currents are generated near the surface, but they
penetrate to greater depths. The relative magnitude and distribution of eddy currents in good and poor conductors are
shown in Figure 4-4.
