Effect of eutectic modification and the solidification rate on the impact strength of a356 aluminum-silicon alloys

The microstructure evolution under elevated plastic deformations was investigated by means of transmission electron microscopy (TEM) in different aluminium alloys processed by the equal channel angular pressing (ECAP) technique in route Bc to strain of 8. The alloys was characterized by submicron-scale grains. The AA1200 high-angle boundaries (misorientation higher than 15°) accounted for ~70% of all boundaries. In the AA5754 measurements indicated average grain sizes of about 0.3-0.4 ìm in the as-pressed condition, thereby demonstrating that ECAP is an especially effective procedure for attaining an ultrafine grain size. It appeared that many of the grain boundaries were illdefined and it is reasonable to assume that, as in an earlier report on ECAP of commercial Al alloys, these boundaries are in high-energy non-equilibrium configurations. For the AA6082 different kinds of alloys have been investigated, the first alloy (commercial AA6082) has a microstructure evolution depending on the presence of Mg2Si and Si particles, the others alloys (with Zr and Sc+Zr) have a microstructure stabilized by the dispersoids