Evolution and Mechanical Effect of S′-Phase in ECA Pressed Al-3.8Cu-1.2Mg-0.5Mn Alloys

The composition, morphology, and distribution of an Al-3.8Cu-1.2Mg-0.5Mn alloy precipitate formed during the ECAP process was investigated using XRD and TEM, and its mechanical properties were estimated via a SP test. A texture structure was formed at the initial state of the ECAP process, but an equiaxed structure was formed as the process progressed. The grain size was refined to around 100 nm through the ECAP process, and the morphology of the S' phase at the initial state is characterized by a rod shape in the grain boundary. As the number of passes increased, the S' phase assumed a spherical shape, with a diameter of 10 rim to 20 nm, and it was uniformly distributed in the internal grain boundary. Growth of the S' phase was also observed, and is thought to be due to Ostwald ripening. The results of the SP test show that the maximum load increased to above 60%, indicating that changes in the size and distribution of the S' phase affect the alloy's tensile strength.