Compressive deformation behavior and energy absorption characteristic of additively manufactured sheet CoCrMo triply periodic minimal surface lattices

Abstract

CoCrMo sheet triply periodic minimal surface (sheet-TPMS) lattices with two different topologies (Neovius, IWP) were fabricated by laser power bed fusion (LPBF). Compressive behavior and energy absorption characteristic for each topology and direction were investigated. The unique pore channel structures of the fabricated Neovius and IWP lattices were well formed. The microstructural observation revealed that fine cellular substructures existed inside the sheets, and most of their constituent phases were confirmed to be the FCC phase. The results of the compression tests demonstrated that Neovius lattice had higher yield strength and first peak strength than IWP lattice, regardless of the compressive direction. As for the stress–strain curves of the lattices, an abrupt stress drop was found in neither of the two topologies. A comparison of the energy absorption characteristics confirmed that Neovius lattice had higher energy absorption efficiency and ideality than IWP lattice. The deformed structures showed that Neovius lattice displayed a gradual collapse mode, whereas a layer-by-layer compaction mode was indicated in IWP lattice. After the deformation, Neovius showed an evenly distributed and high fraction of the HCP phase caused by strain-induced martensitic transformation. The topology of lattice and strain-induced martensitic transformation effects on the compressive mechanical responses of the LPBF-built TPMS lattices were also discussed.