Characterisation of intermetallic particles formed during solution treatment of an Al-7Si-0.4Mg-0.12Fe alloy

► It is concluded in this work that the fine needle-like particles formed during the solution treatment of the 356 type alloy are indeed β phase plates similar to those frequently observed in as-cast aluminium alloys but of much finer sizes, most likely formed by precipitation in the vicinity of the dissolving π phase particles. ► The crystal structure of the needle-like particles, as examined by selected area electron diffraction, can be essentially indexed as either the A-Centred Monoclinic lattice [18] or the Orthorhombic lattice [25]. ► The particles appear to co-exist in two distinct forms: single crystal particles and composite micro-constituent particles.