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Stress-corrosion Cracking of Aluminum Alloys
註釋This memorandum summarizes information submitted in response to a questionnaire distributed by the Aerospace Research and Testing Committee of the Aerospace Industries Association of America. Aluminum alloys most often associated with stress-corrosion cracking in actual service are 2014, 2024, 2219, 7075, 7079, and 7178 alloys, and cast alloys of Ternalloy 7, 40E, 195, and 220 compositions. The tensile stresses necessary to initiate stress-corrosion cracking may be either (1) applied (as through static loads, press fits, or fasteners), or (2) residual (such as from heat treatment or machining). The prevention of failure requires a basic knowledge of the phenomenon and of the relative resistance of the various alloys, and of the effect of grain structure on cracking susceptibility. Application of this knowledge and use of good practices in heat treatment, working, forming, machining, and design can reduce the incidence of stress corrosion. The application of compressive stresses such as by shot peening or the use of coatings offers an effective means of minimizing or at least delaying stress-corrosion cracking. Laboratory investigations of stresscorrosion cracking often involve C-ring or tensile specimens exposed by alternate immersion in 3-1/2 percent NaCl solution. (Author).