Adiabatic heating and role of the intermetallic phase on the ECAP-induced strengthening in an Al-Cu alloy

In the present work, the strengthening effect of the Fe-rich intermetallic phases in a 2219 aluminum alloy subjected to equal-channel angular pressing (ECAP) has been studied. Three different deformation conditions, corresponding to the as-extruded, ECAP/A-1 pass and ECAP/'A-2 passes were considered. Mechanical and morphological characterizations have been performed by microhardness tests, light microscopy, transmission electron microscopy and scanning electron microscopy observations. All the contributions to the strengthening due to solid solution, dislocation boundary and secondary phase have been discussed. The electron microscopy study focused on the evaluation of the strengthening effect generated by the (Fe, Mn, Cr)3Si2Al15 intermetallic. This strengthening effect, generated by coarse precipitates such are the Fe-rich intermetallics, has also been correlated to the morphological particle aspect. The ECAP-induced adiabatic heating strengthening contribution was also determined. A strengthening combination model of all the microstructure terms was proposed and applied to this case to meet the alloy yield stress at the two different ECAP straining levels corresponding to the first and the second pass via route A.