Research Projects

The project aims to develop porous metal-metal interpenetrating phase composites for energy absorption applications. The area of metal-metal interpenetrating phase composites is an emerging area following the rise of additive manufacturing technologies. Custom designed metal or alloy preforms can be infiltrated with a different metal or alloy to fabricate a two phase metal-metal interpenetrating phase composite. Such composites have demonstrated an interesting suite of physical properties. For example, the PI’s research group has successfully produced Zn-(Ti-6Al-4V) and A383-(Ti-6Al-4V) composites and evaluated their mechanical properties. The Ti-6Al-4V in the as-mentioned examples was fabricated using selective laser melting and was designed to have a porous lattice structure into which molten Zn or molten Al alloy was infiltrated. These composites in turn demonstrated an almost 300 and 250% higher compression yield strength than their respective monoliths i.e. Zn and Al alloy respectively. The bulk composites also exhibited a plateau in their stress-strain curve indicating a capability for energy absorption. Hence the energy absorption capabilities can be further enhanced if one of the metal phases is made porous. To the best of our knowledge, there are no published reports of open cell porous metal-metal interpenetrating phase composites, albeit some published reports on porous metal-polymer and porous metal-ceramic interpenetrating composites exist. Our group has recently processed open cell porous metal-metal interpenetrating phase composites (MM-IPCs) in the Zn-(Ti-6Al-4V) system. Preliminary studies revealed that these porous MM-IPCs are demonstrating an extended plateau, a signature of high energy absorption, vis-à-vis the bulk MM-IPCs as well as monolithic Zn. The porous MM-IPC of Zn-(Ti-6Al-4V) is also 37% lighter than its bulk MM-IPC and its energy absorption is almost equal to that of bulk MM-IPC. However detailed investigations involving optimization of the structure and phase distribution are desired to enhance energy absorption tendencies of porous MM-IPCs. Specifically, the impact of porosity, template geometry, phase constitution on the strength and energy absorption capabilities of these porous systems needs to be investigated systematically. This proposal aims at doing that. The porous MM-IPCs of Zn-(Ti-6Al-4V) and A383-(Ti-6Al-4V) will be fabricated using a combination of additive manufacturing and conventional casting techniques. Preform of Ti6Al4V bearing different geometries such as lattice, diamond with different strut wall thickness etc will be processed using selective laser melting. Subsequently the molten metal or alloy of choice such as A383 (Al-9Si-3Zn-2Cu-1Fe) and Zn will be cast into the Ti6Al4V preform. Prior to casting molten metal, a powder bed of salt particles will be introduced into the preform. The salt particles will act as space holders which can leached out later by dissolving in water resulting in a porous MM-IPC. The mechanical behavior of these porous MM-IPCs will be studied using both experimental and finite element modelling (FEM) approaches. The FEM simulations can help optimizing the structure of the porous MM-IPCs by suggesting the amount of porosity, the size and distribution of the pores, the dimensions and geometry of the preform which can yield the desired mechanical performance. Guided by the simulation predictions, the processing of optimized porous MM-IPCs will be carried out and detailed mechanical characterization of the as-fabricated composites will be conducted. Since additive manufactured materials generally result in metastable materials, the effect of heat treatment of the metal template on the overall mechanical performance of the porous MM-IPCs will also be studied.