Delayed fracture studies were conducted on sheet specimens of aluminum alloys 2024 and 7075 in different conditions of temper upon wetting with a liquid 2% zinc amalgam. Delayed fracture data obtained at ambient temperature showed behavior characteristic of this type phenomenon in that the time to failure under sustained load varied inversely to the magnitude of applied stress. Tests on alloys 2024 and 7075 in the precipitation hardened condition revealed that embrittlement could occur rapidly at stress levels below the yield strength of the material while similar tests on these alloys in the annealed state showed that brittle fracture could not be induced at sub-yield stress levels regardless of time held at stress.
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