Damping of NiTi Scaffolds Produced by Selective Laser Melting

Thursday, May 23, 2013: 15:45
Congress Hall 2 (OREA Pryamida Hotel)
Prof. Michael de Wild , University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland
Mr. Fabian Meier , University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland
Mrs. Therese Bormann , University of Basel, Basel, Switzerland
Prof. Bert Müller , University of Basel, Basel, Switzerland
Shape-memory alloys exhibit ultrahigh mechanical damping [1]. Owing to biocompatibility, mechanical strength, and damping capacity [2], NiTi is an important material for medical implants. In this communication, we present the damping characteristics of porous NiTi structures produced by selective laser melting (SLM): The designed microstructures are layer-by-layer fabricated by means of a laser that locally melts the dedicated powder. This approach allows creating microstructure of complex shapes with interconnected pores, as required for scaffolds in tissue engineering. Furthermore, one can tailor the stiffness within one construct via the porosity [3]. The damping properties of NiTi bars were analyzed by the decay of free vibrations as a function of the temperature [4], which was tracked with a high-speed camera. The logarithmic decrement of damping and the Young’s modulus were derived. The damping ratio shows distinct values at temperatures below austenite start T < As, corresponding to the austenite peak T ≙ Ap and above austenite finish T > Af. This result indicates that medical implants from NiTi with ultrahigh mechanical damping properties can be produced and their optimal working temperature can be verified by DSC measurements.

[1]       J. S. Juan, M. L. No and C. A. Schuh, Nanoscale shape-memory alloys for ultrahigh mechanical damping, Nature Nanotechnology 4, 415-419 (2009).

[2]       T. Xing, et al., Transformation and Damping Characteristics of NiTi/NiTi Alloys Synthesized by Explosive Welding, Materials Transactions, 47, 3, 658-660 (2006).

[3]       R. Schumacher, A. Yildiz, M. Näf, M. de Wild, E. Schkommodau, Manipulation of the elastic behaviour of artificial titanium bone grafts, European Cells and Materials 22 Suppl. 1, 10 (2011).

[4]       H.C. Lin, et al., Damping characteristics of TiNi shape memory alloys, Metallurgical Transactions  24A, 2189-2194 (1993).

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