Functional graded NiTi manufactured with powder bed fusion
Rico Weber, Enrico Tosoratti, Adriaan B. Spierings, Konrad Wegener
Abstract
Abstract Nickel–titanium (NiTi) is a versatile material with unique inherent properties, such as shape recovery, superelasticity, and biocompatibility, that makes it suitable for various engineering applications. While NiTi can be additively manufactured using powder bed fusion for metals (PBF-LB/M), challenges arise due to the material sensitivity to process parameters and the challenge of achieving desired mechanical and functional properties. Mechanical and functional properties of NiTi are highly influenced by the alloy composition which in turn is affected by the process parameters. This study aims to investigate the feasibility of tailoring the properties of NiTi to manufacture functionally graded structures. Promising shape recovery strains of 4.16 $$\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>%</mml:mo> </mml:math> and superelastic strains of 7 $$\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>%</mml:mo> </mml:math> under compression are achieved with cycling stability outperforming the conventional manufactured NiTi. By varying the process parameters, the austenite finish temperature could be shifted between 29 ± 5 $$^\circ$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C and 72 ± 5 $$^\circ$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C, while achieving a maximum relative material density of 99.4 $$\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>%</mml:mo> </mml:math> . Finally, the study demonstrates the potential of powder bed fusion to manufacture complex and functional graded structures, enabling spatial control. This potential is showcased through the sequential actuation of a demonstrator structure. The findings of this research highlight the promising capabilities of powder bed fusion in producing functional graded NiTi structures, with potential applications in robotics, aerospace, and biomedical fields.