Morphological Evolution of Al-2wt%Si-2.5wt%Cu Alloy Produced by EMS and EMS Enhanced by ECAP

Abstract

This work evaluates the morphological evolution at the semisolid state of the Al-2wt%Si-2.5wt%Cu alloy produced by direct chill casting under electromagnetic stirring (EMS) and this same raw material enhanced by one equal channel angular pressing pass (ECAP), specially designed to produce raw material for thixoforming processes. The traditional EMS production method is compared to ECAP in order to determine if a second procedure is necessary for this particular alloy. The ECAP process emerged as a promising technique capable of imposing severe homogeneous deformation in metals, which could improve thixoforming processes. The ECAP deformation occurs in a matrix that contains two channels of the same cross-sectional area and form an angle of Φ = 90° and Φ = 120°, the process can be repeated many times allowing to control the microstructure and properties of the materials. Both raw materials, EMS and EMS + ECAP were submitted to re-heating treatment in two conditions of solid fractions, 45% and 60% at soaking times of 0s, 30s and 90s. With this procedure primary particle sizes of about 60 μm were obtained, which exhibit favourable characteristics for the thixoforming process.