Microstructure, mechanical behavior and stress corrosion cracking susceptibility in ultrafine-grained Al-Cu alloy

Equal-channel angular pressing (ECAP) is capable of improving the mechanical properties of many aluminum alloys by means of intense grain refinement. Meanwhile, a general relationship between grain size and stress corrosion cracking (SCC) resistance is not yet established, since the introduction of microstructural heterogeneities affects, in many ways, the localized corrosion susceptibility. This work evaluates the simultaneous impact of ECAP processing on microstructure, mechanical strength and SCC resistance of an Al-4wt.%Cu alloy, in comparison with a commercially pure aluminum. Microstructure was observed by optical and electronic microscopy, while mechanical response was evaluated by hardness measurements and tensile tests. SCC resistance was evaluated by slow strain rate tests and by constant load tests performed in an aqueous solution with 3.5 wt.% NaCl. ECAP promoted grain refinement, breakdown/redistribution of coarse secondary phase particles and contributed to reduce the local chemical heterogeneity. Consequently, mechanical properties and SCC resistance were simultaneously improved. (AU)