Dispersion of TiH2 Foaming Agent in Precursors via Melt Route

Abstract

The dispersion of TiH2 particles stirred into an Al-9Si melt, to produce a precusor for subsequent foaming, has been studied. The effects of processing parameters have been related to measured changes in the viscosity of the melt. The results show that 610°C is the key point in the temperature - viscosity relationship. Below 610°C, the viscosity increases greatly with decreasing temperature and only above this temperature, when the viscosity increases slowly with temperature, can good dispersions be obtained. The uniformity of the foaming agent dispersion is improved by increasing the melt temperature, stirring speed and stirring time. However, clusters of foaming agent still exist with rotational speeds of 3000rpm and stirring for 30s. Extrusion of the precursor can be used to improve the uniformity of the foaming agent such that very few foaming agent clusters exist and the variation in foaming agent concentration with position in the precursor is very small.