Influência de coberturas salinas em moldes cerâmicos na microestrutura de uma liga Al-Cu.

Abstract

The advantages of effective grain refinement are: Improved feeding characteristics, increased tear resistance, improved mechanical properties, increased pressure tightness, improved response to thermal treatment, and improved appearance following chemical, electrochemical, and mechanical finishing. All aluminum alloys can be made to solidify with a fully equiaxed, fine grain structure through the use of suitable grain-refining addition. The most widely used grain refiners are master alloy of titanium, or of titanium and boron, in aluminum. The objective of the present work was to verify the influence of salts coating in ceramic moulds in microstructure of the Al-40%Cu alloy, and to compare with other sample cooled in a metallic mold. The salts used for the cover of the ceramic mould were 3 salts (LiF, LiCl+LiF), that can to modify the physical-chemical properties of the mould surface, acting as possible agents nucleantes. The alloy had no addition of the titanium-boron based grain size. The results showed the ceramic mould that used LiF+LiCl as salt coating produced a larger microstructural refined, probably for larger interaction physical-chemistry of this salt with the alloy. However, the sample cooled in cooper mold produced a microstructural refined larger than salt coating.