Macro-segregation in aluminium alloy sprayformed billets

It is generally assumed that during sprayforming the amount of micro- and macro-segregation in the sprayforms will be limited or absent because of low liquid fractions, small grain size and high cooling rate. This paper shows that macro-segregation can occur in sprayforms of Al, even when small liquid fractions are present during growth of the sprayform. This segregation occurs by an inverse mechanism, with solute-rich liquid sucked back through a solid network by solidification shrinkage. Liquid flow outwards is further enhanced by the centrifugal force produced by sprayform rotation. The liquid sucked outwards is enriched in solute (with partition coefficients