表面肝素改性TLM钛合金的血液相容性评价(英文)

在新型近β钛合金TLM(Ti-3Zr-2Sn-3Mo-25Nb)表面用溶胶-凝胶法镀上一层TiO2薄膜,再将薄膜依次用羟基化溶液和胺基化溶液处理以在薄膜表面引入活性OH-和NH2-,然后通过该活性官能团将肝素共价键接在薄膜表面。利用XRD、SEM和EDS研究了TiO2薄膜的相结构和表面特性;通过测定材料表面的接触角、溶血率和血小板黏附行为对肝素化TLM合金的血液相容性进行分析、评价。结果表明,表面肝素化处理后TLM合金的血液相容性得到了明显的改善。

Haemocompatibility of Ti-3Zr-2Sn-3Mo-25Nb biomedical alloy with surface heparinization using electrostatic self assembly technology

The haemocompatibility of Ti-3Zr-2Sn-3Mo-25Nb biomedical alloy was studied after surface heparinization. A layer of sol-gel TiO2 films was applied on the alloy samples followed by active treatment in the bio-functionalized solution for introducing the OH- and groups, and then the heparin was immobilized on the active TiO2 films through the electrostatic self assembly technology. It is shown that the heparinized films are mainly composed of anatase and rutile with smooth and dense surface. In vitro blood compatibility was evaluated by haemolysis test, clotting time and platelet adhesion behavior tests. The results show that the haemocompatibility of the alloy could be significantly improved by surface heparinization.

CF/Al复合材料横向拉伸渐进损伤与弹塑性力学行为

针对真空压力浸渗制备的单向碳纤维增强铝合金复合材料(CF/Al复合材料),采用细观力学数值模拟与实验结合的方法研究了其横向拉伸损伤演化和断裂力学行为,并分析了界面对复合材料横向拉伸力学性能的影响。结果表明,基于基体合金延性损伤和界面内聚力损伤本构所建立的细观单胞有限元模型,可以实现CF/Al复合材料横向拉伸弹塑性力学响应的计算和预测。复合材料横向拉伸时先后发生界面损伤、界面失效以及基体损伤累积与失效现象,界面损伤脱粘并诱发基体塑性损伤和失效是导致复合材料横向断裂的主要机理。增加界面强度有利于提高横向拉伸屈服强度和极限强度,界面刚度对极限强度影响不大,但增加界面刚度可有效提高复合材料横向拉伸弹性模量。

A comparative study of the role of solute,potent particles and ultrasonic treatment during solidification of pure Mg,Mg-Zn and Mg-Zr alloys

Ultrasonic treatment(UST)applied during the solidification of pure Mg,eutectic(Mg-Zn)and peritectic(Mg-Zr)alloys was investigated in order to explore the grain refinement mechanisms.Temperature dependent grain refinement is observed in pure Mg where decreasing the superheat temperature(at which UST is applied from above the melting temperature,TM)from 100℃to 40℃produces significant refinement with a uniform grain structure.The presence of solute reduces the temperature dependence of the UST refinement and excellent grain refinement is obtained regardless of the superheat temperature(100℃or 40℃)and even with the use of preheated sonotrode in the Mg-6 wt.%Zn alloy.A further improvement in grain refinement is achieved when the alloy contains potent particles that introduce additional nucleation of grains in Mg-0.5 and 1.0 wt.%Zr alloys(producing an average grain size of≤100μm).At 40℃superheat,UST of Mg-Zn alloys produces excellent refinement(average grain size<200μm)with non-dendritic grains,which is normally achieved only with the addition of grain refining master alloy in the as-cast condition.The enhanced refinement observed in the eutectic alloy is explained through the undercooling imposed by a relatively cold sonotrode combined with high frequency vibrations and acoustic streaming.The advantages of using a cold sonotrode,a low superheat and solute are demonstrated for achieving significant refinement during solidification of Mg alloys under UST without or with a lower addition of grain refining master alloys.

Microstructure modification and corrosion resistance enhancement of die-cast Mg-Al-Re alloy by Sr alloying

The effects of Sr additions on the microstructure and corrosion performance of a Mg-Al-RE alloy in 3.5 wt.%Na Cl saturated with Mg(OH)_(2) have been investigated.Microstructure examination reveals that the Sr addition introduces additional intermetallic phases,refines intermetallic networks and dendritic grains,and improves the network continuity.More Al and rare earth elements can be identified in the intermetallics and grain boundaries or inter-dendrite regions under a transmission electron microscope and secondary electron microscope,respectively.On the Sr-containing intermetallic phases and the refined microstructure,the oxide films become more protective,resulting in more corrosion resistant boundary areas and thus dendrite grain grooves.Hence,the presence of large amounts of intermetallics and boundaries can enhance the corrosion performance of the Mg-Al-RE alloy containing Sr.

Surface modification of biomedical Mg-Ca and Mg-Zn-Ca alloys using selective laser melting: Corrosion behaviour, microhardness and biocompatibility

Magnesium alloys such as Mg–Ca and Mg–Zn–Ca are good orthopaedic materials;however their tendency to corrode is high.Herein we utilize selective laser melting(SLM)to modify the surface of these Mg alloys to simultaneously improve the corrosion behaviour and microhardness.The corrosion rate decreased from 2.1±0.2 mm/y to 1.0±0.1 mm/y for the laser-processed Mg–0.6Ca,and from 1.6±0.1 mm/y to 0.7±0.2 mm/y for laser-processed Mg–0.5Zn–0.3Ca.The microhardness increased from 46±1 HV to 56±1 HV for Mg–0.6Ca,and from 47±3 HV to 55±3 HV for Mg–0.5Zn–0.3Ca.In addition,good biocompatibility remained in the laser processed Mg alloys.The improved properties are attributed to laser-induced grain refinement,confined impurity elements,residual stress,and modified surface chemistry.The results demonstrated the potential of SLM as a surface engineering approach for developing advanced biomedical Mg alloys.

Effect of corrosion inhibiting compounds on the corrosion behaviour of pure magnesium and the magnesium alloys EV31A, WE43B and ZE41A

This paper studied corrosion of pure Mg and the Mg alloys EV31A,WE43B,ZE41A,coated with commercial corrosion inhibiting compounds(CICs)(LPS 3,LPS2,AMLGuard,Ardrox 3961)immersed in 3.5 wt%(0.6M)Na Cl solution saturated with Mg(OH)_(2).All four CICs reduced corrosion rates.LPS 3 resulted in zero corrosion rates and 100%inhibition in most cases.LPS 2 and AMLGuard had comparable inhibition efficiencies,whilst Ardrox 3961 had the lowest inhibition efficiency.Reduction in corrosion rates was tentatively attributed to barrier films formed by chemical adsorption for LPS 3 and AMLGuard,and by physical adsorption for LPS2 and Ardrox 3961.

Stress corrosion cracking of high-strength AZ31 processed by high-ratio differential speed rolling

Stress corrosion cracking(SCC)in distilled water was studied for AZ31,processed by differential-speed-rolling to different strengths,using Linear Increasing Stress Tests(LISTs).The stress corrosion crack velocity was 5.0±2.5×10^(−9) m s^(−1),independent of applied stress rate and independent of material strength.SCC susceptibility was greater at lower applied stress rates manifest most importantly as a lower threshold stress for stress corrosion crack initiation.SCC susceptibility could be characterised by the ratio of threshold stress to yield stress,which was dependent on processing details and was as low as 0.3.

医用钛合金表面TiO2覆膜生物改性的研究

在新型近β钛合金Ti-3Zr-2Sn-3Mo-25Nb表面分别用3种微弧氧化法(普通微弧氧化、复相微弧氧化、紫外照射微弧氧化)和优化溶胶-凝胶法镀上一层TiO2薄膜,考察了各种薄膜的表面微观结构、与基体的结合强度以及亲水性和抗腐蚀性能。XRD和SEM测试结果表明,3种微弧氧化膜主要由金红石相和锐钛矿相组成,表面布满微孔,普通微弧氧化法和紫外光照射微弧氧化法制备的薄膜表面较为光滑,与基体的结合强度为53 MPa,略高于复相微弧氧化膜;溶胶-凝胶膜主要由锐钛矿组成,表面最为光滑致密,与基体的结合强度为32 MPa。接触角测试结果表明,紫外光照射微弧氧化膜的表面亲水性最好,溶胶-凝胶膜的亲水性要好于普通微弧氧化膜和复相微弧氧化膜;电化学腐蚀试验显示,4种TiO2薄膜都具有较好的抗腐蚀性能,而普通微弧氧化膜的抗腐蚀能力最好。

2.5维织物C_f/Al复合材料制备及其经纬向拉伸变形力学行为研究

以石墨纤维2.5维机织物为增强体,铝合金ZL301为基体材料,采用真空辅助压力浸渗法制备了2.5维织物Cf/Al复合材料,研究了3种织物预热温度下制备的复合材料相对致密度和微观组织形貌,分析了其界面产物组成与界面结构特征,测试了其经、纬向准静态拉伸变形力学行为并分析了其断口形貌。结果表明:复合材料织物的细观结构完整,内部纤维分布均匀,致密度随预热温度提高而略有上升,界面棒状产物为Al4C3相,其相对含量随预热温度的提高而增加,从而引起复合材料经向和纬向力学性能的下降。复合材料经向拉伸强度高于纬向拉伸强度,且其应力-应变行为呈现出显著的非线性特征,复合材料经向和纬向拉伸变形过程均可划分为3个阶段:初始弹性变形阶段、中间弹塑性变形阶段和最终损伤与断裂阶段。

Current understanding of the origin of equiaxed grains in pure metals during ultrasonic solidification and a comparison of grain formation processes with low frequency vibration,pulsed magnetic and electric-current pulse techniques

The formation of fine,non-dendritic equiaxed grains throughout a casting without the addition of refiners(i.e.independent of alloy chemistry),is made possible by using ultrasonic,magnetic or pulsed magnetic and electric current pulse techniques.The dominant mechanisms proposed for the grain refinement produced during the application of an external field are cavitation phenomena assisted nucleation or fragmentation of dendrites(ultrasonic field),wall crystals arising from the cold surface of the mould(electric current pulse,magnetic and pulsed magnetic fields).In all these cases fluid flow provides an additional contribution(e.g.reduced temperature gradients,growth rate and remelting of dendrites)to maintaining an equiaxed grain structure.The origin of equiaxed grains under an external field also depends on the casting conditions(volume and shape of casting)and the type of alloy other than the mechanisms specific to a particular technique.The current work aims to provide a detailed understanding of the various factors and mechanisms that influence the grain refinement achieved during the solidification of pure metals(magnesium and zinc)subjected to Ultra Sonic Treatment(UST).The role of the temperature range of UST application,time duration and an unpreheated sonotrode are examined with respect to the origin,evolution of equiaxed grain structure,morphology and the columnar to equiaxed transition.The origin of grains was analysed from three fundamental aspects that contribute to refinement(i)heterogeneous nucleation(ii)fragmentation of existing dendrites and(iii)grains produced from the colder surfaces(arising from mould walls or vibrating surfaces as wall crystals).A comparison of UST refinement with mechanical,low-frequency vibration,electric current pulse and magnetic field solidification of pure metals has also been provided to highlight the importance of the cold surfaces(sonotrode and mould wall)in influencing grain refinement.

In vivo performance of a rare earth free Mg-Zn-Ca alloy manufactured using twin roll casting for potential applications in the cranial and maxillofacial fixation devices

A magnesium alloy containing essential,non-toxic,biodegradable elements such as Ca and Zn has been fabricated using a novel twin-roll casting process(TRC).Microstructure,mechanical properties,in vivo corrosion and biocompatibility have been assessed and compared to the properties of the rare earth(RE)element containing WE43 alloy.TRC Mg-0.5 wt% Zn-0.5 wt% Ca exhibited fine grains with an average grain size ranging from 70 to 150μm.Mechanical properties of a TRC Mg-0.5Zn-0.5Ca alloy showed an ultimate tensile strength of 220 MPa and ductility of 9.3%.The TRC Mg-0.5Zn-0.5Ca alloy showed a degradation rate of 0.51±0.07 mm/y similar to that of the WE43 alloy(0.47±0.09 mm/y)in the rat model after 1 week of implantation.By week 4 the biodegradation rates of both alloys studied were lowered and stabilized with fewer gas pockets around the implant.The histological analysis shows that both WE43 and TRC Mg-0.5Zn-0.5Ca alloy triggered comparable tissue healing responses at respective times of implantation.The presence of more organized scarring tissue around the TRC Mg-0.5Zn-0.5Ca alloys suggests that the biodegradation of the RE-free alloy may be more conducive to the tissue proliferation and remodelling process.

High strength and ductility of titanium matrix composites by nanoscale design in selective laser melting

The use of selective laser melting(SLM)to produce titanium matrix composites(TMCs)with high strength while retaining sufficient tensile ductility suitable for structural applications is emerging as an attractive opportunity in the field of advanced manufacturing.However,the presence of coarse ceramic reinforcements as well as difficulties in optimizing the SLM process is a barrier to the application of TMCs.In this study,we demonstrated the production of TMCs reinforced with in situ high aspect ratio Ti B nanowhiskers by selective laser melting using nanosized BN powder additions.Pure Ti with 2.5 vol.%nanosized BN powder showed promise for producing high performance TMCs with retained ductility.BN acted to produce Ti B nanowhiskers with diameter<50 nm.Further,by controlling post process furnace annealing Ti B retained a low diameter but exhibited a high aspect ratio,up to 400.In addition to Ti B refinement,nanosized BN addition promoted grain refinement during SLM,both acting as a solute to induce nucleation events and,as Ti B is formed,providing nucleation sites leading to an ultrafine grain structure in as printed samples and after annealing.The produced TMCs exhibit high tensile yield strength,up to1392 MPa,while retaining tensile ductility up to 10%.This study has shown how nanoscale design in powder bed fusion additive manufacturing techniques can be used to produce high performance TMCs through a combination of refined grain structure and high aspect ratio Ti B leading to TMCs with significant improvement in strength,isotropic properties and retained tensile ductility.

A state-of-the-art review on passivation and biofouling of Ti and its alloys in marine environments

High strength-to-weight ratio, commendable biocompatibility and excellent corrosion resistance make Ti alloys widely applicable in aerospace, medical and marine industries. However, these alloys suffer from serious biofouling, and may become vulnerable to corrosion attack under some extreme marine conditions. The passivating and biofouling performance of Ti alloys can be attributed to their compact, stable and protective films. This paper comprehensively reviews the passivating and biofouling behavior, as well as their mechanisms, for typical Ti alloys in various marine environments. This review aims to help extend applications of Ti alloys in extremely harsh marine conditions.