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.