Shear deformation of high solid fraction (>0.60) semi-solid SnPb under various structures

The behavior of high solid fraction (>0.60) semi-solid SnPb alloys was studied in pure shear deformation using a Couette geometry rheometer. Three structures were investigated: a classical coarse dendritic structure, a globular structure obtained by reheating a fine dendritic structure (R.G.) and a globular structure generated by vigorous stirring during solidification (S.G.). The slurries were subjected to shear rates ranging from 0.01 to 50 s−1. Experimental data for dendritic structure and for R.G. are compared to the model proposed by Nguyen et al. (Proc. 2nd Int. Conf. on Processing of Semi-Solid Alloys and Composites, Boston, USA, 1992, p.296; and Int. J. Plast. 10 (1994) 693). The S.G. structure exhibited a very different behavior compared with globular structures obtained from a fine dendritic precursor (R.G.). This behavior is interpreted in terms of an agglomeration/disagglomeration model.