Fabrication of multi-functional Ni-Ti alloys by laser powder bed fusion

Ni-Ti alloys with multiple transformation temperatures for a single component can be called multi-functional Ni-Ti alloys. Multi-functional Ni-Ti alloys can increase the flexibility of designing complex systems and have broad application prospects. Existing research mainly focuses on manufacturing multi-functional Ni-Ti alloys through welding or changing the local Ni/Ti ratio. However, the above-mentioned methods have problems such as the low connection strength of the welded part, difficulty of precisely controlling the Ni-Ti ratio, and poor design flexibility. In this paper, laser powder bed fusion (LPBF) was used to successfully fabricate multi-functional Ni-Ti alloys. Ni-rich (Ni53.4-Ti46.6 (at.%)) powders and Ti-rich (Ni46.4-Ti53.6 (at.%)) powders were prepared. The Ni-rich powder was first used to fabricate super-elasticity (SE) parts with a high relative density. The Ti-rich powder was then used to manufacture shape memory effect (SME) parts with different process parameters based on the SE parts. These integrated components were processed into dog-bone shapes and subjected to tensile tests. The sample that had the highest ultimate tensile strength while manufactured at a relatively low energy density was selected for further analysis. The properties of the sample, such as the microstructure and transformation temperature, were analysed through a series of tests. The results confirm that LPBF is a suitable method to fabricate multi-functional Ni-Ti alloys.

Automated summary

The study successfully fabricated multi-functional Ni-Ti alloys using laser powder bed fusion (LPBF) method, by sequentially manufacturing super-elasticity and shape memory effect parts with Ni-rich and Ti-rich powders, respectively. Tensile tests were conducted on integrated components to select the sample with the highest ultimate tensile strength at a relatively low energy density for further analysis of microstructure and transformation temperature, confirming LPBF as a suitable method for fabricating multi-functional Ni-Ti alloys.