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Fatigue properties of a new generation ß-type Ti-Nb alloy for osteosynthesis with an industrial standard surface condition

 
: Reck, André; Pilz, Stefan; Cǎlin, Mariana; Gebert, Annett; Zimmermann, Martina

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International journal of fatigue 103 (2017), S.147-156
ISSN: 0142-1123
Deutsche Forschungsgemeinschaft DFG
M1
Englisch
Zeitschriftenaufsatz
Fraunhofer IWS ()
Ti-Nb alloy; metallic implant; fatigue properties; laser cutting; osteosynthesis plates

Abstract
This research work focuses on the fatigue behavior of a new metastable Ti-40Nb alloy (wt.%) with a single ß-phase microstructure and a low Young’s modulus of 60 GPa. Samples were manufactured by laser cutting and subsequently subjected to an anodized (Type III) surface condition which is currently an industrial standard (Stryker Trauma GmbH). Accompanied by detailed analysis of the fractured surfaces by means of scanning electron microscopy (SEM) including cross section preparation by means of focused ion beam (FIB) at the crack initiation area, the experimental results reveal a large scatter and a fatigue strength of 150 MPa at 2 × 106 cycles (R = −1). In-depth surface evaluation before and after the fatigue tests show a variety of large notches distributed along the complete sample radius as a consequence of the laser cutting process. Stress concentration on these surface flaws together with the notch sensitivity of titanium alloys are the major reason for the pronounced scatter of fatigue results accompanied by crack initiation always starting from the surface. Equally tested cp-titanium (ASTM Grade 4) reference samples exhibit a fatigue strength of 200 MPa at 2 × 106 cycles. Additionally studied osteosynthesis plates of Ti-40 Nb and cp-4 titanium (hand surgery sector – same surface condition) showed even lower fatigue strength compared to the standard fatigue specimens.

: http://publica.fraunhofer.de/dokumente/N-452557.html