Abstract
The stress-corrosion cracking (SCC) behavior of an Al-2.9Cu-2.2Li-0.12Zr alloy was investigated in 3.5% NaCl solution. The alloy was tested in the peak-strength condition and in two overaged tempers. The SCC velocity as a function of the stress intensitiy factor K I was obtained by testing precracked double cantilever beam (DCB) specimens in alternate immersion. Slow-strain rate experiments were also conducted in air and total immersion by using smooth cylindrical specimens. The results from both testing methods show that the degree of susceptibility depends on the aging condition, the peak-aged temper being the most resistant. Overaging induces susceptibility owing to the development of strain at the grain boundaries. This strain is a result of phase interactions and transformations and is produced by the preferential T 1 precipitation at grain boundaries, the cutting of δ′ by growing φ′ and the consequent transformation of φ′ to T 1. Possible embrittlement mechanisms are discussed.
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