Selective Laser Melting of TiNi Auxetic Structures

This talk details the pathway for the development of TiNi-based negative Poisson's ratio structure using selective laser melting (SLM). The SLM process-ability of Ti-rich TiNi was explored, revealing a high susceptibility to cracking and the formation of Ti2Ni intermetallics, as well as oxygen pick-up during the process. Process optimisation, by varying the process parameters, resulted in a significant reduction of cracking and porosity. Nonetheless, post-process heat treatments were essential to improve the microstructural homogeneity of the builds, and to reduce the Ti2Ni intermetallics to achieve the appropriate shape memory performance. Furthermore, optimisation of the auxetic structure via Finite Element Modelling (FEM) was used in order to design the target Poisson's ratio, with the SLM processed structure having a similar performance as predicted by FEM.