A fractographic examination was made of unnotched aged and solution treated Ti-8Al specimens subjected to fluctuating tension fatigue in air, 3% aqueous NaCl, and methanol-HCl. Crack initiation in air and 3% NaCl probably occurred from reversed slip. Crack initiation in methanol-HCl was by intergranular dissolution. Corrosion along slip bands was observed to be a secondary process in bulk specimens, but is the main process in thin foil stress corrosion. Cycling of the crack tips into compression induced twinning, which modified the appearance of transgranular stress corrosion. The transition from transgranular stress corrosion to Stage IIa fatigue was well defined and was probably caused by plastic blunting of the crack tip.
© 1973 National Association of Corrosion Engineers
1973
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