Controlling size and shape of pores during metal solidification for manufacturing of functionally graded metal foams

Abstract

Manufacturing of metal foams by solidification processing involves numerous challenges related to achieving localized control of porosity with a limited material selection. The objective of this work is to control the size and shape of pores during metal solidification in a casting process by harnessing the thermal decomposition of discrete polymer features upon their interaction with molten metal. The influence of geometrical parameters and physical properties of these features on the evolution of pores generated from their interaction with molten metal was studied in detail. We firstly used an analytical model to evaluate the thermal response of such features in a model molten metal medium to determine the process window within which pores can be generated and captured in place during metal solidification. Systematic experiments were conducted to demonstrate the influence of the feature geometry on the evolution of the size and shape of captured pores. We further demonstrate that the relative separation of these features can exert a strong influence on the interaction of adjacently generated pores during metal solidification. This work essentially exhibits the potential of exploiting a lattice of discrete features that can enable the spatial control of pore capture during a metal solidification process.