| Summary: | 碩士 === 長庚大學 === 機械工程學系 === 98 === Aluminum alloys have been widely used in various applications, including being used in different kinds of corrosive environments. The objective of this study is to reduce the growth of stress corrosion cracking of AA6061 in chloride-containing environment via various thermomechanical processing.
The experimental results indicate that rapid quenching after solution heat treatment may possibly retard the formation of precipitate-free zones (PFZ) along the grain boundaries, and subsequently reduce the growth of stress corrosion cracking. Overaging of the alloy may alter the distribution of the precipitates in the matrix and grain boundaries, and result in more severe growth of the intergranular cracking.
As long as the AA6061 alloy is heat treated with T6 temper, the intergranular cracking cannot be successfully limited to the acceptance criterion, which is less than 200 µm deep underneath the sample surface. When the samples are forged to different degrees at room temperature prior to aging heat treatment, the characteristic of cracking becomes pitting instead of intergranular, and the penetrating depths of cracking are always significantly lower than 200 µm. It has been concluded that the T8 temper with various degrees of cold work can successfully retard the growth of stress corrosion cracking of AA6061 in the chloride-containing corrosive solution.
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