Intergranular corrosion of coarse- and fine-grain high strength aluminum alloy before and after cryogenic rolling

The intergranular corrosion (IGC) resistance of the 1965 aluminum alloy with complex transition metal (TM) additions before and after thermomechanical treatment of the homogenized ingot, including quenching, severe isothermal hot multidirectional forging and cryogenic rolling, and natural aging, was investigated. The alloy structure and the characteristics of the IGC lesions found at all stages of its treatment were studied using conventional methods of optical and scanning electron microscopy. The structural factors involving the morphology of the phase components, the dispersion and defectiveness of the matrix, the distribution of primary and secondary phases in its volume, as well as the precipitate free zones, which controlled the nature of the alloy IGC with equilibrium and highly deformed structures, were discussed. It was found that forging resulted in a slight increase in the alloy IGC resistance, which was mainly affected by grain and excess phase refinement and breaking of the continuous grain boundary network of TM aluminide precipitate free zones formed during homogenization. In contrast, the significant IGC improvement of both the cast and forged alloy was observed after cryorolling with more than twice less total and uniform corrosion depth. The latter was due to the high work-hardening effect resulting from the formation of a developed dislocation-cellular structure inside elongated grains with excess phase strings along their boundaries and uniformly distributed precipitates of TM aluminides.

1. Russian Science Foundation - 23-19-00702