Investment casting of periodic aluminum cellular structures using slurry-cast table salt moulds

Abstract

A process is presented for the production of periodic cellular structures based on investment casting of Al-12 wt%Si alloy within a mould that is made of table salt (NaCl) packed around a sacrificial PLA polymer template. Moulding begins by pouring salt grains suspended within brine and packed by vibration around the pattern. This is followed by draining, drying, and pyrolysis of the polymer followed by pressure infiltration of the resulting mould with molten metal. Cast Al-12 %Si structures made of octahedra linked at their vertexes (6 in all three directions) with a relative density of 31% are produced and characterized for their microstructure and compressive deformation. The highly porous structures replicate accurately the polymer pattern in dense metal, have a compressive modulus of 1.2 GPa, a plateau stress of 20 MPa, a densification strain of 77%, and an energy absorption of 15 J/cm3 corresponding to an efficiency of 80% compared to an ideally plastic material.

Keywords

• Investment casting
• Freeform manufacturing
• Periodic cellular structures
• NaCl
• Salt mold
• AlSi12