The results indicated that there is a greater amount of porosity in modified alloys, and that modified alloys need less H than unmodified alloys to nucleate
The experiments determined two basic nucleation mechanisms of the eutectic phase - the eutectic nucleates
directly on the primary aluminum dendrites and the eutectic nucleates
on the existing substrate particles in the melt.
In general, microcellular processing consists of first forming a polymer/gas solution followed by the inducement of a rapid thermodynamic instability, which simultaneously nucleates a very large number of microvoids (2, 4-9).
This follows since cells will preferentially nucleate at the limited number of high energy interfaces such as additive particles, crystalline phases, contaminants, and pigments.
The most powerful nucleates
for hydrogen precipitation are oxides--especially those that trap gaseous phases through turbulence in gating, pouring, melt handling and treatment.