摘要
为研究分析细晶表面对Ti3Zr2Sn3Mo25Nb(TLM)钛合金生物力学相容性的影响,引入机械方法对TLM钛合金表面进行表面改性。振幅30μm,冲击数分别为24000和48000次·mm^(-2)下对TLM钛合金进行超声表面冲击纳米化处理。跟未处理试样结果比照,对超声冲击表面处理前后的表面形貌、强塑性变形层、模拟体液中的极化曲线、腐蚀形貌、表面沉积物、预腐蚀后的疲劳行为等进行分析。TLM钛合金表层生成了纳米晶,细晶生成机制主要为位错滑移;钙磷等元素表面矿化沉积加强;尽管细晶表面轻微弱化了TLM钛合金耐体液腐蚀的性能,模拟体液预浸泡后TLM钛合金1×10^(7)周次的疲劳强度仍有显著提升且幅度超20%;表面细晶存在与否、模拟体液的腐蚀对疲劳强度的影响均较小;单位面积冲击次数越大提升幅度越大;内部萌生裂纹常出现在数百微米深粗晶变形层内α相滑移汇集的三叉晶界处,且裂尖塑性区略大于晶粒平均尺寸,表现为沿晶塑性起裂。
To study the effect of fine grain surface on the biomechanical compatibility of Ti3Zr2Sn3Mo25Nb(TLM),ultrasonic impact with mechanical methods was applied to modify the surface. TLM was a novel β-type titanium alloy which was developed by Northwest Nonferrous Metal Research Institute in Xian,China. Due to the big content(nearly a quarter of mass)of element niobium and the regulating of molybdenum,β-phase was stable in the microstructure of TLM titanium alloy. Thus,its elastic modulus was much similar to human bones,and this was beneficial to reduce the stress shielding. The stress field could be gradual and continuous with the tiny difference of elastic modulus between the metal implants and bones. Surface self-nanocrystallization(SSN)had become a research hot spot in the recent two decades. With SSN,the elastic modus was lower than base material. Surface modification by means of ultrasonic impact(UI)was developed by Huawin Hauck-energy Technology Co,Ltd in Jinan,China. The surfaces of metals were remodeled with only surface impact,which was different from UNSM(ultrasonic nanocrystallization surface modification,an international patent of Korea). For the domestic titanium implant alloy,more basic researches should be done to optimize the database for the clinical application,such as the application of UI on TLM titanium alloys. Nanocrystal surface modification with mechanical methods on metal implants was an originality which could help them to be large-scale industrial manufactured. Meanwhile,this technology was easier to form standards. The effect of fine grains on the biocompatibility of TLM titanium alloys was investigated,including the corrosion behavior in simulated body fluid(SBF,complied with Kokubo recipe),the deposition of the main osteogenesis minerals,and the fatigue properties. Two groups were separated,with the different strike number per square millimeter of 24000 and 48000 times(mentioned as UI-24000 and UI-48000),with an amplitude of 30 μm. The other group without UI treatment was for contrast. For the fatigue test,totally six groups of specimens were divided(with or without the influence of SBF). Rotating bending fatigue was completed with a stress ratio of-1. The surface topography,severe plastic defornation layer,polarisation curve in SBF,corrosion feature,surface depositions,and the corrosion fatigue behavior of TLM titanium alloys which was pre-soaked into SBF for four weeks were studied. Transmission electron microscopy(TEM) images showed that ultra-fine grains(with the size of several nano meters) were induced by the repeated shock The nano crystal layer was with a depth of tens of microns. More strike number generated more deeper severe plastic deformation layer;the depth of nano layer was about 35 μm for UI-48000. Because the slip crystal systems abounded in body centered cubic β-crystals(totally twelve slip directions),the mechanism of generating nano grains in the surface of TLM titanium alloys was the dislocation glide. The surface flatness was decreased slightly after ultrasonic surface impact treatment. More strike number gained more smoother surface topography. The average value of UI-18000 was approximately 0.22 μm. At the same while,the current density of corrosion was increased and the pitting corrosion is accelerated. The corrosion resistance was decreased due to the superficial expansion with plastic overflow and the promotion of the surface-active energy. As the increase of strike number,the attenuation of corrosion potential was more and more obvious. The corrosion rate of nano grain surface was about three times of which with no surface treatment.The depositions of minerals such as calcium,phosphorus,sodium and chlorine on nano grain surface were improved with different levels. The improvement of Ca and P was advantageous for the rehabilitation after bone replacement,because they two were osteogenesis elements. Phosphorus was more easily adsorbed on the nano grain surface than calcium. In the game of fatigue,corrosion and reinforcement,ultrasonic impact improved the fatigue strengths of TLM titanium alloys subjected to SBF to over 20%,from 380 to 470 MPa.The influence of SBF on the fatigue strength was negligible because the fatigue strength losses of specimens with nano grain surface were less than 5%. The strength of TLM titanium alloys specimens without UI treatment decreased about 10%,from 380 to 340 MPa.The inner cracks usually appeared at the trigeminal grain boundary where slips converged together. The crack cores distributed with the depth range of 200~500 μm. The fatigue strength could be improved higher with more strike number per unit. Comparing with the group without any treatment,more inner cracks appeared at lower fatigue cyclic stress due to the surface modification. For the specimens subjected to UI,the penetration of corrosion in SBF was observed,in special the elements chlorine and sodium. The combination of the inner slip and the tip corrosion caused the fracture together. The propagation of micro cracks in the crack core acted as intergranular plastic initiation. The size of crack tip plastic zone was a little bigger than the average grain size. Thus,the faint change of stress intensity factor might slow down the crack initiation. To evaluate the effect of ultrasonic impact treatment on metal implants,the overall investigation should be investigated.
作者
金胡日查
沈吴钦
许家婧
曹小建
王清远
Jin Huricha;Shen Wuqin;Xu Jiajing;Cao Xiaojian;Wang Qingyuan(The Second Affiliated Hospital of Nantong University,Nantong 226000,China;School of Transportation&Civil Engineering,Nantong University,Nantong 226019,China;School of Mechanical Engineering,Nantong University,Nantong 226019,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2022年第9期1190-1198,共9页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(11802145)
南通市科技计划指导性项目(JCZ19024)
南通市基础科学研究项目(JC2021170)资助。
