Effect of Edge-Modified Parameters and Heat Treatment on Ni50.4Ti49.6 LPBF Trabecular Structures for Biomedical Applications

Abstract

Among smart materials, nickel-titanium (NiTi) alloys stand out as one of the most widely employed materials for biomedical devices. This is largely due to its unique properties, such as superelasticity and shape memory effect, as well as its biocompatibility. The growing demand for personalized medical devices with mechanical and structural performances increasingly resembling natural human bone has positioned additive manufacturing (AM) as the preferred technology to meet these needs, enabling the production of complex, patient-specific architectures that traditional methods cannot efficiently achieve, such as trabecular structures. These architectures have been demonstrated to promote improved osseointegration at the implant-bone interface. However, the combined challenges of AM processes and the complex behavior of NiTi require careful choices to fully exploit the potential of this approach. In particular, the alloy is very sensitive to printing parameters, which can cause surface defects and varying levels of porosity. This study investigates how local adjustment of laser parameters at the structure edges, together with heat treatment (HT), affects Ni_50.4Ti₄₉.₆ trabecular architectures produced using laser powder bed fusion (LPBF). Three different sets of parameters were examined: one homogeneous (H) and two modified conditions at the edges (EM1, EM2) that had varying energy densities at the edges, higher and lower, respectively. The influence of energy input and heat treatment on chemical composition, transformation temperatures, porosity, surface morphology, and mechanical performance was systematically evaluated. The results showed that adjusting the energy at the edges helped reduce surface defects and composition differences, while heat treatment helped stabilize the austenitic phase (A_f < 25 °C), enabling superelastic behavior at room temperature. The combination of homogeneous energy input and post-AM heat treatment provided well-balanced overall performance, increasing compressive failure force and a stable oxide formation, whereas edge-modified conditions improved surface characteristics that may be beneficial for osseointegration. These results highlight that accurate adjustment of LPBF parameters and heat treatment can lead to the fabrication of NiTi trabecular structures with optimized structural and functional properties, suitable for advanced and more customizable implant applications.