| Autor: |
Lam, I., Ganot, G., Brundage, D., Velcheck, L., Deacon, R., Marder, A. |
| Zdroj: |
Journal of Failure Analysis & Prevention; Feb2006, Vol. 6 Issue 1, p32-38, 7p |
| Abstrakt: |
Various aluminum parts, both castings and rolled sheet, were found among the Columbia debris. At first glance, these parts seemed to have failed in a brittlelike manner, contrary to normal aluminum fracture behavior. Light optical microscopy on the etched aluminum samples examined in this study revealed second-phase particles along the grain boundaries. It was also observed that at the elevated temperatures encountered during re-entry, some of the particles melted and wetted the grain boundaries. Large voids could be found between the grains near the crack tips. Energy-dispersive spectroscopy showed particles that were rich in iron. During re-entry of the shuttle, elevated temperatures caused melting of the second-phase particles, allowing them to wet the grain boundaries, a process called liquation. Cracks initiated and propagated through the grain boundaries, thus resulting in intergranular rupture that had the macroscopic characteristics of brittle failure of the aluminum. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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