超声表面冲击对Ti6Al4V生物相容性的影响

Because the difference of elastic modulus between titanium alloy implants and human bones is large,prosthetic loosening and osseous change usually happen due to the stress shielding.Though bioactive films are coated onto the Ti-base implants for the clinical application,the thickness is limited several microns.Therefore it is necessary to search a method,which can improve the biocompatibilities and smooth the stress gradient.Ultrasonic surface impact (ultrasonic nanocrystal surface modification,UNSM) was carried out with the condition of a static load of 25 N,vibration amplitude of 30 μm and 36 000 strikes per unit on Ti6Al4V.The surface topography,severe plastic defornation layer,polarisation curve in simulated body fluid (SBF),corrosion feature,surface depositions,corrosion fatigue behavior of Ti6Al4V which was pre-soaked into SBF for two weeks,and the adhension of fibrochondrocyte were studied.A depth of 40 μm nanocrystal surface layer is achieved.UNSM improves the fatigue strengths of Ti6Al4V in SBF though the current density of corrosion is increased and the pitting corrosion is accelerated.Inner cracks usually appear at coarse grained deformation layer between the depth of 100~250 μm,because the residual compressive stress is reduced and the toughness is lower than the surface.Calcium and phosphorus nodules are significantly enhanced on UNSMed surface.The earlier adhension of fibrochondrocyte can be promoted at the same while.Coating a TiN film on the UNSMed surface helps to improve the whole biocompatibilities of Ti6Al4V further.The gradient of elastic modulus and grain size are helpful to resist stress shielding.Hybrid surface modification has positive significance for metal implants.