Electrochemical characteristics of nanotubes formed on Ti-Nb alloys

Titanium and Ti alloys have been used extensively as bone-implant materials due to their high strength-to-weight ratio, good biocompatibility and excellent corrosion resistance. In this work, we have investigated the effects of the β-stabilizing element Nb on the morphology of nanotubes formed on Ti-xNb alloys using 1.0 M H₃PO₄ electrolyte containing 0.8 wt.% NaF and various electrochemical methods. Oxide layers consisting of highly ordered nanotubes with a wide range of diameters (approximately 55-220 nm) and lengths (approximately 730 nm-2 μm) can be formed on alloys in the Ti-xNb system as a function of Nb content. The nanotubes formed on the Ti-Nb alloy surface were transformed from the anatase to rutile structure of titanium oxide. The titanium oxide nanotube surface was observed to have lower corrosion resistance in 0.9% NaCl solution compared to titanium oxides surfaces on Ti-xNb alloys without the nanotube morphology.     

Effect of fluoride on the corrosion behavior of nanostructured Ti-24Nb-4Zr-8Sn alloy in acidulated artificial saliva

The surface of titanium dental implants is highly susceptible to aggressive fluoride ions in the oral environment. Nanotechnology has proven an effective approach to improve the stability and corrosion resistance of titanium by applying a passive film. In this study, we investigated the effects of fluoride on the corrosion behavior of nanostructured(NS) Ti-24 Nb-4 Zr-8 Sn(Ti2448) alloy in acidulated artificial saliva(AAS)at 37 ℃, and then conducted comparisons with its coarse grained(CG) counterpart. Electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), as well as surface analysis including X-ray photoelectron spectroscopy(XPS) with argon ion sputtering, and scanning electronic microscopy(SEM) were employed to evaluate the effects of fluoride on sensitivity to pitting and the tolerance of Ti2448 to fluoride in AAS solution. The results demonstrate that corrosion current density increased with F-concentration. In all respects, the NS Ti2448 alloy presented corrosion resistance superior to that of its coarse grained(CG) counterpart at low F-concentrations(0.1%).Furthermore, a high content of F-(1%) was shown to promote the active dissolution of both alloys by increasing the rate of corrosion. Following immersion in the fluoridated AAS solution for 60 days, a tissuefriendly compound, Ca_3(PO_4)_2, was detected on the surface of the NS when F-= 0.01% and Na_2 TiF_6 was identified as the main component in the corrosion products of the CG as well as NS Ti2448 alloys when F-= 1%. High concentrations of F-produced pitting corrosion on the CG alloy, whereas NS Ti2448 alloy presented general corrosion in the form of lamellar separation under the same conditions. These findings demonstrate the superior corrosion resistance of the NS Ti2448 alloy as well as lower pitting sensitivity and higher tolerance to fluoride due mainly to grain refinement.     

微弧氧化处理对钛铌合金力学及摩擦磨损性能的影响

采用微弧氧化的方法于磷酸盐电解液中在二元β型TiNbx(x=5,10,15,20,25)合金表面制备了微弧氧化涂层.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)表征各合金表面微弧氧化涂层的物相组成和微观形貌.采用纳米压痕仪、球-盘摩擦磨损实验仪分析了微弧氧化处理对钛铌合金力学性能、耐磨性的影响.结果表明,通过微...     

Recent advances on environmental corrosion behavior and mechanism of high-entropy alloys

In the past decade,the sudden rise of high-entropy alloys (HEAs) has become a research hotspot in the domain of metal materials.HEAs break through the design concept of traditional single-principal element alloys,and the four core effects,especially the high entropy and cocktail effects,make HEAs exhibit much better corrosion resistance than traditional corrosion-resistant metal materials,e.g.,stain-less steels,copper-nickel alloys,and high-nickel alloys.Currently,the corrosion resistance of HEAs causes great concern in the field of corrosion research.This article reviews the corrosion behavior and mechanism of HEAs in various aqueous solutions,revealing the correlation among the composition,microstructure and corrosion resistance of HEAs,and elaborates the influence of heat treatment,anodizing treatment and preparation methods on the corrosion behavior of HEAs.This knowledge will benefit the on-demand design of corrosion-resistant HEAs,which is an important trend of future development.Finally,perspec-tives regarding the corrosion research of HEAs are outlined to guide future studies.     

Revisiting the effects of molybdenum and tungsten alloying on corrosion behavior of nickel-chromium alloys in aqueous corrosion

Minor alloying additions such as molybdenum (Mo) have major effects on the localized corrosion resistance of corrosion resistant alloys containing chromium. However, progress in alloy development is mostly based upon empirical observations, where any mechanistic insights are largely relegated to the latter stages of localized corrosion (i.e., stabilization and propagation) that are more readily accessible experimentally. For instance, it is well understood that Mo and tungsten (W) affect repassivation of local active, as well as widespread transpassive, corrosion sites and Mo surface enrichment during corrosion is well-documented. In this paper, a comprehensive examination of the functions and mechanism by which selected Mo and W operate to improve the passivity and resistance to breakdown during the initial stages of localized corrosion of the most common Ni-based solid solution alloys is presented. It is shown that Mo and W exert considerable influence on many stages of corrosion, including both passivation and film breakdown, re-enforcing old and introducing more recent ideas in this comprehensive review of the current state of corrosion research on Ni-Cr-(Mo + W) alloys.     

Comparative corrosion study of Ag-Pd and Co-Cr alloys used in dental applications

The electrochemical behaviour of two Ag-Pd alloys (Unique White and Paliag) used in dental prosthetics construction for crowns and bridges and one Co-Cr alloy (Vitallium 2000) was studied in artificial saliva using the polarization curves and electrochemical impedance spectroscopy (EIS). The corrosion resistance was evaluated by means of the corrosion currents value and by coulometric analysis. The open circuit potential of Ag-Pd are attributed to dealloying followed by surface enrichment with Ag and the possible formation of an insoluble AgCl surface film on the respective alloy surfaces. Our results have shown that these alloys have a somewhat good corrosion resistance in artificial saliva. The corrosion current densities of Unique White and Vitallium 2000 alloys were very low (∼100 nA/cm²). For Ag-Pd alloys, when increasing the content of Cu, corrosion resistance decreases. The passivation of all samples occurred spontaneously at the open circuit potential. The electrochemical properties of the spontaneously passivated electrodes at the open circuit potential were studied by EIS. The polarization resistance (R _p) and the electrode capacitance (C _dl) were determined. The polarization resistance of all the samples increases with the immersion time. The polarization resistances are largest for Unique White (Ag-Pd) and Vitallium 2000 (Co-Cr) alloys. Because the electrochemical behaviour of the Co-Cr alloy was compared with that of Ag-Pd alloy, this type of alloy may be a suitable alternative for use in the manufacture of fixed dental prostheses. The present study, though limited, has shown that electrochemical characteristics can be used to identify such alloys. Knowledge of the in vitro corrosion behaviour of these alloys may lead to better understanding of any biologically adverse effects in vitro.     

Predicting the degradation behavior of magnesium alloys with a diffusion-based theoretical model and in vitro corrosion testing

Magnesium alloys have shown great potential for their use in the medical device field, due to the promising biodegradability. However, it remains a challenge to characterize the degradation behavior of the Mg alloys in a quantitative manner. As such, controlling the degradation rate of the Mg alloys as per our needs is still hard, which greatly limits the practical application of the Mg alloys as a degradable biomaterial. This paper discussed a numerical model developed based on the diffusion theory, which can capture the experimental degradation behavior of the Mg alloys precisely. The numerical model is then implemented into a finite element scheme, where the model is calibrated with the data from our previous studies on the corrosion of the as-cast Mg-1Ca and the as-rolled Mg-3Ge binary alloys. The degradation behavior of a pin implant is predicted using the calibrated model to demonstrate the model’s capability. A standard flow is provided in a practical framework for obtaining the degradation behavior of any biomedical Mg alloys. This methodology was further verified via the comparison with enormous available experimental results. Lastly, the material parameters defined in this model were provided as a new kind of material property.     

Electrochemical study of the corrosion behavior of Ce sealing of anodized 2024 aluminum alloy

The technological process of Ce sealing of anodized LY12 (2024) alloy is introduced in this paper. The corrosion behavior of the film is studied by polarization curves and electrochemical impedance spectroscopy. The results show that the coating remains passive at the potential range from the open circuit potential (−780 mV) to −250 mV. After immersing the sample in NaCl solution for 6 days, the outer layer Ce conversion coating begins to loose its anticorrosive property. The inner Ce sealing anodized film is not corroded until 60 days immersion. Thus, the inner layer Ce sealing anodized film takes the leading role of the corrosion protection for LY12 alloy.     

Microstructure and corrosion behaviour of FeCoNiCuSnx high entropy alloys

Abstract

The FeCoNiCuSn_x alloys with different Sn contents are prepared, the microstructure and the corrosion behaviour of the alloys are investigated. When Sn content is lower than 0.09, FeCoNiCuSn_x alloys consist of a single FCC phase. While Sn content of the alloy is 0.09, a small quantity of BCC structure is present. The FeCoNiCuSn_x alloys have a wider passive region in the NaOH solution. FeCoNiCuSn_x alloys exhibit a better corrosion resistance in NaCl solution than 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.04 alloy is best among all the alloys. The corrosion resistance of FeCoNiCuSn_x alloys in NaOH solution is lower than that of 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.03 alloy is best among all FeCoNiCuSn_x alloys.     

Effect of aging treatment on microstructure and corrosion behavior of Al-Zn-Mg aluminum alloy in aqueous solutions with different aggressive ions

The microstructure and corrosion behavior of Al-Zn-Mg alloy(namely 7×××)after natural aging treatment(NAT)and artificial aging treatment(AAT)in aqueous NaCl solutions containing different aggressive ions have been investigated in current work.Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates.The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT.The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy(EIS).The corrosion potential(E_corr)of the aluminum alloy is more negative in 3.5 wt.%NaCl containing 0.052 wt.%NaHSO₃solution than that in 3.5 wt.%NaCl solutions with or without 0.907 wt.%NaHCO₃.Charge transfer resistance(Rct)results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT.With the immersion time increasing,mostly pitting spreads over the surface of the alloy only in NaCl solution,whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO₃or NaHCO₃.     

Effect of applied potential on the microstructure,composition and corrosion resistance evolution of fluoride conversion film on AZ31 magnesium alloy

AZ31 magnesium (Mg) alloy was potentiostatic polarized in 0.1?M deaerated KF solution with pH 7.5 from ?0.4?V to ?1.4?V with an interval of ?0.2?V. The polarization process was described by the potentiostatic current decay. The resultant film was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The results demonstrated that the deposited film included a Mg(OH)₂/MgF₂ containing inner layer and a Mg(OH)₂/MgF₂/KMgF₃ comprising outer layer. The high polarized potential produced high content of MgF₂ but low content of KMgF₃ and thin film. Conversely, the low polarized potential produced small content of MgF₂ but high content of KMgF₃ and thick film. The optimal corrosion resistance of the deposited film was obtained at ?1.4?V, which was closely related with the content of MgF₂ and KMgF₃ and the film thickness.     

生物医用镁合金腐蚀行为的研究进展EI北大核心CSCD

近年来,镁合金作为生物可降解材料受到了越来越多研究者的关注,由于其具有良好的生物相容性、力学性能及可降解吸收等特点,被誉为一种“革命性的生物材料”。然而,由于腐蚀速率过快和存在局部腐蚀的缺点,目前的生物镁合金仍达不到临床应用的要求。本文从高纯化、合金化、热处理工艺、表面改性等方面综述了最近几年生物镁合金在提高腐蚀性能方面的研究进展,并从添加无毒性合金元素,适当的表面涂覆,先进的制备技术及热处理工艺方面,对如何研制出腐蚀性能更好的生物可降解材料进行了展望。     

The estimation of corrosion behaviour of ZrTi binary alloys for dental applications using electrochemical techniques

Titanium and zirconium are in the same group in the periodic table of elements and are known to have similar physical and chemical properties. Both Ti and Zr usually have their surfaces covered by a thin oxide film spontaneously formed in air. However, the cytotoxicity of ZrO₂ is lower than that of TiO₂ rutile. Treatments with fluoride are known as the main methods to prevent plaque formation and dental caries. The corrosion behaviour of ZrTi alloys with Ti contents of 5, 25 and 45 wt.% and cp-Ti was investigated for dental applications. All samples were tested by linear potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) performed in artificial saliva with different pH levels (5.6 and 3.4) and different fluoride (1000 ppm F⁻) and albumin protein (0.6%) contents. In addition, scanning electron microscopy (SEM) was employed to observe the surface morphology of the test materials after linear potentiodynamic polarisation. The corrosion current densities for the ZrTi alloys increased with the titanium content. The Zr5Ti and Zr25Ti alloys were susceptible to localised corrosion. The role that Ti plays as an alloying element is that of increasing the resistance of ZrTi alloy to localised corrosion. The presence of 0.6% albumin protein in fluoridated acidified artificial saliva with 1000 ppm F⁻ could protect the cp-Ti and ZrTi alloys from attack by fluoride ions.     

非晶态Ni—Si—B系合金在FeCl3溶液中的腐蚀行为

用失重法研究了几种Ｎｉ－Ｓｉ－Ｂ系合金在ＦｅＣｌ３溶液中腐蚀行为，分别考查了腐蚀速率与材料组分，表面状态，溶液温度，浓度及ｐＨ值的关系。结果表明：随着Ｎｉ含量增加，表面状态越粗糙，溶液浓度增加，温度升高，ＰＨ值降低，均将使腐蚀速率增加。     

Investigation of glass-forming ability,deformation and corrosion behavior of Ni-free Ti-based BMG alloys designed for application as dental implants

We developed new Ti-based bulk metallic glassy (BMG) alloys in Ti–Zr–Pd–Cu–Sn system without Ni element for application as biomaterials. These BMG alloys have a high potential to be applied as metallic biomaterials in various forms, such as melt-spun ribbons and cylindrical rods with a diameter of 4 mm. We also investigated of new Ti-based BMG alloys with higher glass-forming ability (GFA) for medical market as dental implants. These Ti-based BMG alloys do not contain Ni, Al and Be elements which are well known to be harmful for human body. In particular, a rod sample of the Ti_44.1Zr_9.8Pd_9.8Cu_30.38Sn_3.92Nb₂ BMG alloy with a diameter of 3 mm produced by copper mold casting exhibits a compressive strength of 1990 MPa and a Young's modulus of 99 GPa. In addition, the Ti_44.1Zr_9.8Pd_9.8Cu_30.38Sn_3.92Nb₂ BMG shows a large supercooled liquid region of 62 K and a reduced glass-transition temperature, T_rg( = T_g / T_m) of 0.61. The high thermal stability of the supercooled liquid allowed the fabrication of cylindrical rod specimens up to 5 mm in diameter. Thus the studied alloy exhibits high glass-forming ability (GFA) and a large size enough to be used for dental implants. The Ti_44.1Zr_9.8Pd_9.8Cu_30.38Sn_3.92Nb₂ BMG alloy also has a high corrosion resistance and is passivated at the lower passive current density of approximately 10^? 2 A m^? 2, 10^? 3 A m^? 2 and 10^? 2 A m^? 2, in 1 mass% lactic acid, PBS (phosphate-buffered saline without calcium and magnesium salts solution) and HBSS (Hank's balance salt solution without calcium, magnesium and phenol red), respectively, at 310 K, which are lower than those of pure Titanium and Ti–6Al–4V alloy.     

Cr含量对CrMnFeNi系高熵合金腐蚀行为的影响EI北大核心CSCD

利用XRD,SEM/EDS,EBSD,电化学测试等表征手段研究Cr含量对Cr_(x)MnFeNi(x=0.8,1.0,1.2,1.5)高熵合金微观组织与耐蚀性能的影响。结果表明:Cr_(0.8)MnFeNi高熵合金为单相FCC结构,Cr_(x)MnFeNi(x=1.0,1.2,1.5)高熵合金为FCC+BCC双相结构,且BCC相比例随着Cr含量升高而增加。在0.5 mol/L H_(2)SO_(4)溶液中,高熵合金的耐蚀性能随着Cr含量降低而增强,其中,Cr_(0.8)MnFeNi单相高熵合金的耐蚀性能最好,这是因为Cr_(0.8)MnFeNi高熵合金的成分更为均匀。此外,Cr_(x)MnFeNi高熵合金在0.5 mol/L H_(2)SO_(4)溶液中均具有宽泛的钝化区域以及明显的伪钝化区域,表明合金在耐蚀性能上具有较大的研究价值和开发潜力。     

Research on the microstructure,fatigue and corrosion behavior of permanent mold and die cast aluminum alloy

Permanent mold (PM) and high pressure die cast (HPDC) AlMg5Si2Mn are employed to investigate the microstructure, fatigue strength and corrosion resistance. Results indicated that the mechanical properties (R_m, R_0.2 and δ) of HPDC specimens (314 MPa, 189 MPa and 7.3%) are significantly better than those of PM specimens (160 MPa, 111 MPa and 2.5%) due to the finer grain size and less cast defects. Fatigue cracks of PM samples dominantly initiated from shrinkage pores and obscure fatigue striations are observed in crack growth region. Corrosion and pitting potentials of PM and HPDC AlMg5Si2Mn alloy are around −1250 mV, −760 mV and −1220 mV, −690 mV respectively. Numerous pits are observed around the grain boundaries because the corrosion potential of Mg₂Si is more anodic than that of α-Al matrix. In addition, the superior corrosion resistance of HPDC samples can be attributed to the fine grain size and the high boundary density which improved the formation of oxide layer on the surface and prevented further corrosion.     

Corrosion behavior of AZ91 magnesium alloy in dilute NaCl solutions

The corrosion behavior of AZ91 magnesium alloy in dilute NaCl solutions was studied using electrochemical measurements, whereby a corrosion map in terms of electrode potential and chloride concentration [Cl⁻] was obtained. AZ91 alloy exhibited the corrosion and passivation zones in dilute NaCl solutions. The passivation zone became narrow with increasing [Cl⁻]. The values of open-circuit potential were in the passivation zone when the [Cl⁻] was less than 0.5 mol/L. XRD patterns showed the presence of the Mg(OH)₂, Mg₅(CO₃)₄(OH)₂·8H₂O and MgO phases in the corrosion product, whereas the latter two phases found in the passive film.     

Influence of Fluoride Content of Artificial Saliva on Metal Release from 17-4 PH Stainless Steel Foam for Dental Implant Applications

Highly porous 17-4 PH stainless steel foam for implant applications was produced by space holder technique. Metal release and weight loss from 17-4 PH stainless steel foams were investigated in fluoride added artificial saliva environment by static immersion test.An inductively coupled plasma-mass spectrometer was employed to measure the concentrations of various metal ions.Effects of fluoride content of artificial saliva on metal release and weight loss from the steel foams were investigated.Effects of immersion time,pH value and process parameters on the weight loss and metal release were determined.Pore morphology,pore size and mechanical properties of the 17-4 PH stainless steel foams were also characterized.     

Comparative study of martensitic transformation behavior of NiAlMn and NiAlMnFe high temperature shape memory alloys

A comparative study of microstructure and martensitic transformation (MT) behavior of Ni₅₉Al₁₁Mn₃₀ and Ni₆₀Al₁₉Mn₁₆Fe₅ high temperature shape memory alloys (SMAs) has been performed by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), optical microscopy, and micro-hardness testing. The MT temperature (MTT) of Ni₅₉Al₁₁Mn₃₀ alloy is higher than that of Ni₆₀Al₁₉Mn₁₆Fe₅ alloy, and both alloys’ MTT increases with increasing annealing temperature. The temperature hysteresis and hardness of Ni₅₉Al₁₁Mn₃₀ alloy are smaller than that of Ni₆₀Al₁₉Mn₁₆Fe₅ alloy. The MT behavior of Ni₆₀Al₁₉Mn₁₆Fe₅ is sensitive to aging temperature and its MTT and hysteresis decrease with increasing aging temperature. However, the MT behavior of Ni₅₉Al₁₁Mn₃₀ alloy is not sensitive to aging temperature. The MT stabilization effects appear in both alloys during thermal cycles. This stabilization effect vanishes from the second thermal cycle. The quenched microstructure of Ni₅₉Al₁₁Mn₃₀ and Ni₆₀Al₁₉Mn₁₆Fe₅ alloys is M plus gamma phase, in which the volume fraction of gamma phase is about 40 and 20%, respectively, and the microhardness of M is higher than that of gamma phase. No aging effects were found in both alloys after aging at 400 °C.