Influence of Pre-Solution ECAP and Ag Content on the Microstructure and Mechanical Properties of As-Cast Al–Cu–Mg–xAg Alloys

Casting-related microstructural variations can affect the mechanical performance of Al–Cu–Mg–Ag alloys. This study examines a novel processing route in which a single equal channel angular pressing (ECAP) pass was introduced before solution treatment (Route 2) and compares it with conventional heat treatment (Route 1) for alloys containing 0.3 and 0.6 wt.% Ag. Increasing the Ag content from 0.3 to 0.6 wt.% increased the hardness after solution treatment from 93 to 109 HV. Ageing at 190 °C further increased strength, with the 0.3 wt.% Ag alloy processed by Route 2 showing the highest tensile performance, with a UTS of 317 MPa and an approximately 14% elongation. Optical and electron microscopy showed a finer and more uniform microstructure in the ECAP-processed condition, together with differences in the morphology and distribution of second-phase constituents. The fracture surfaces also differed markedly between the two routes. The peak-aged Route 1 condition showed predominantly intergranular fracture associated with precipitate-free zones and coarse grain-boundary intermetallic particles, whereas Route 2 showed a more ductile fracture surface with numerous deep, equiaxed dimples formed by microvoid coalescence. These results show that introducing ECAP before solution treatment can improve the mechanical and fracture behavior of Al–Cu–Mg–Ag alloys and offers a useful alternative to the conventional processing sequence.