On the formation of spheroidal microstructures in a semi-solid Al-Si alloy by thermomechanical processing

Spheroidal microstructures suitable for thixoforming, can be formed by a variety of techniques. From optical microscopy and electron backscattered diffraction observations, the mechanism of formation of such microstructure in an Al-Si alloy conditioned by the so-called deformation-recrystallization technique is described as an internal partition of the deformed dendrites. During heating and partial remelting, low angle boundaries turn into high angle boundaries, whose penetration by the liquid is energetically favorable, thus leading to a dispersion of spheroidal Al-alpha particles. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.