A characterization of microstructure and microhardness on longitudinal planes of an Al–Mg–Si alloy processed by ECAP

An AA6005 Al–Mg–Si alloy was used to investigate the evolution of microhardness and microstructure on the longitudinal or Z planes after processing by ECAP where these planes lie parallel to the upper and lower surfaces of the billet. The processing was conducted at a temperature of 423 K using an ECAP die with a channel angle of 90°. Samples were pressed for up to 8 passes and observations were undertaken on the top and bottom planes and on a parallel plane located at approximately the center of the billet. The results show that the grain size is reduced from ~ 50 μm in the initial condition to ~ 200 nm after 8 passes with similar grain sizes recorded on all three planes of observation. Measurements of the microhardness show the values increase by a little more than two times after 8 passes. The results from this investigation demonstrate that excellent microstructural homogeneity may be achieved throughout the Al–Mg–Si billet after processing through a total of 8 passes.