The effect of severe plastic deformation on precipitation in supersaturated Al–Zn–Mg alloys

Experiments were conducted to examine the influence of equal-channel angular pressing (ECAP) on the development of precipitation microstructures in two supersaturated Al–Zn–Mg alloys. The results show that ECAP leads to an ultrafine grain size with finely dispersed η precipitates. It is concluded that processing by ECAP promotes the precipitation processes because dislocations act as nucleation sites for precipitates. Spherical precipitates were observed in the alloys processed by ECAP whereas long rod-like precipitates were also observed after ageing without ECAP. Calculations show the yield strengths estimated from the characteristic parameters of the precipitation microstructure are in good agreement with the values determined by mechanical testing.