| Description |
vii, 84 leaves : illustrations ; 28 cm |
| Summary |
"Electrical conductivity measurements (eddy current determined) combined with indentation hardness measurements are now being used throughout the aerospace industry for nondestructive evaluation of the metallurgical condition of commercial precipitation hardenable aluminum alloys. The review of literature and experiments with two aluminum alloys, 7178 and a 5% Zn-Al binary, have shown that skilled interpretation of hardness-conductivity data depends not only upon a qualitative understanding of the modern wave mechanical theories of electron conduction, but also upon some knowledge of the precipitation reaction kinetics. In particular, the effects of "quenched-in" vacancies and retrogression upon the reaction kinetics must be considered. Studies of conductivity vs temperature in the range of 0 to 75°F show that the resulting conductivity changes do not result in increased interpretative information and the Matthiessen's rule and Hansen's equation both apply. Hansen's equation relates conductivity (K) of a sample to its temperature coefficient of resistance ([alpha]) in the form of K = B[alpha] + C where B and C are constants. The values of B and C depend only upon the alloy system being considered. A practical result is that the conductivity for an unknown sample can be evaluated at any known ambient temperature and then corrected to its room temperature value by calculating the sample's coefficient of resistance using Hansen's equation. The inverse calculation could also be made"--Abstract, leaf ii. |
|
