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"What we usually consider as impossible are simply engineering problems...there's no law of physics preventing them."
ASME International Mechanical Engineering Congress & Exposition (IMECE)-2022
October 30–November 3, 2022
Columbus, Ohio, USA
There has been a growing interest in fabricating porous NiTi structures, which have potential applications in tissue engineering, impact absorption, and fluid permeability.
Conventional manufacturing methods face challenges when fabricating NiTi structures due to poor machinability, high work hardening, and springback effects. Additive manufacturing (AM) can address these challenges.
AM enables the production of complex NiTi structures, including metallic scaffolds and porous architectures, with intricate details.
Triply periodic minimal surface (TPMS) structures have gained attention, but there is limited research on fabricating NiTi TPMS structures and understanding their behavior. The complex geometries of these structures can influence the melt pool dynamics and solidification rate, impacting the microstructure of the fabricated parts.
Inhomogeneity in microstructures was observed in fabricated parts, prompting a detailed examination of these structures.
The novelty of the study lies in investigating the influence of NiTi TPMS lattice geometries and laser process parameters.
TPMS Structures
Additive Manufacturing of NiTi TPMS structures
Cu based Shape memory effect
NiTi Schwarz TPMS layers were 3D printed using LPBF, with varying relative densities and scanning strategies.
Balling was observed in all samples, particularly pronounced at 60% relative density and inclined scan strategy, accompanied by intergranular crack formation.
Microstructure analysis indicated non-uniform solidification rates, but no clear trends were found with density or scanning strategy.
Spattering of the melt pool was identified as a potential cause for balling on the printed structures.
Surface quality plots for NiTi TPMS samples of a) primitive and b) gyroid topologies
NiTi shape memory alloys pose challenges in machining due to their high ductility and superior strength.
Additive Manufacturing (AM) provides a viable solution by eliminating the need for tooling and allowing intricate structures.
The study focuses on fabricating architected triply periodic minimal surface (TPMS) lattices using laser powder bed fusion (LPBF).
Primitive and gyroid topologies are explored in the fabrication process.
Geometric properties and process parameters significantly influence microstructural characteristics and solid phase distribution in the samples.
Process parameters and structural topology have a substantial impact on the microstructural features.
Observations are made about nickel evaporation and the formation of oxide- and titanium-rich phases in relation to their distance from the base plate.
Investigating intricate TPMS geometries in NiTi alloys with varying laser process parameters is a relatively new and unexplored research area.
These geometries may offer unique structural and functional properties, leading to innovative applications and advancements in various fields.