Compression fatigue behavior of laser processed porous NiTi alloy.

Porous metals are being widely used in load bearing implant applications with an aim to increase osseointegration and also to reduce stress shielding. However, fatigue performance of porous metals is extremely important to ensure long-term implant stability, because porous metals are sensitive to crack propagation even at low stresses especially under cyclic loading conditions. Herein we report high-cycle compression-compression fatigue behavior of laser processed NiTi alloy with varying porosities between ∼1% and 20%. The results show that compression fatigue of porous NiTi alloy samples is in part similar to metal foams. The applied stress amplitude is found to have strong influence on the accumulated strain and cyclic stability. The critical stress amplitudes associated with rapid strain accumulation in porous NiTi alloy samples, with varying relative densities, were found to correspond to 140% of respective 0.2% proof strength indicating that these samples can sustain cyclic compression fatigue stresses up to 1.4 times their yield strength without failure.