Study On The Construction And Preparation Of Regular Porous Foam Metals

This paper deals with a new technique for making regular porous metals using plaster investment casting process. Wax pattern with corresponding porous structure which is designed based on molding function of CAD software is formed with rapid prototyping (RP) technology, and soluble plaster is used as molding material.In experiments, three kinds of regular structures are designed, including diamond-type, tetrakaidecahedron and rhombic dodecahedron structure. By analyzing geometric relationships among structures and using UG sketch and expression functions, full-parametric driving models are created which is the basis of structure finite element analysis and casting pattern rapid prototyping. Then taking diamond-type structure for example and choosing circular cross-section as the pillar's cross-section, formula for relative density is derived with structure representative element model. The deformation morphology and equivalent elastic modulus with small strains are obtained using finite element method under a periodical boundary condition. The relationship between relative modulus and relative density is achieved in light of the curve fitting function of Origin software. The patterns of three structures are developed by selective laser sintering (SLS) technology with PS pattern material. Plaster mixture is prepared on the basis of the high-temperature linear shrinkage characteristics and strength requirements. Calcination process is designed according to the relationship between decomposition of pattern material and temperature through PS-modulus material TGA curve, also taking calcination characteristics of plaster mould into consideration. .And at the same time 13.8% water-soluble salt (MgSO₄) is put in the plaster mixture, which improves plaster water-solvability and casting cleaning efficiency. Finally, porous aluminum (ZL102) is made successfully by vacuum casting process.The result shows that, with great success, the designed process based on CAD/RP technology overcome structure irregularity, low process controllability and properties fluctuation in the former processes for porous foam metals preparation.