Galvanic corrosion behavior of titanium implants coupled to dental alloys

The corrosion of five materials for implant suprastructures (cast-titanium, machined-titanium, gold alloy, silver-palladium alloy and chromium-nickel alloy), was investigated in vitro, the materials being galvanically coupled to a titanium implant. Various electrochemical parameters E_CORR, i_CORR Evans diagrams, polarization resistance and Tafel slopes) were analyzed. The microstructure of the different dental materials was observed before and after corrosion processes by optical and electron microscopy. Besides, the metallic ions released in the saliva environment were quantified during the corrosion process by means of inductively coupled plasma-mass spectrometry technique (ICP-MS). The cast and machined titanium had the most passive current density at a given potential and chromium-nickel alloy had the most active critical current density values. The high gold content alloys have excellent resistance corrosion, although this decreases when the gold content is lower in the alloy. The palladium alloy had a low critical current density due to the presence of gallium in this composition but a selective dissolution of copper-rich phases was observed through energy dispersive X-ray analysis. ©2000 Kluwer Academic Publishers     

Comparative study on the corrosion behavior of Ti-Nb and TMA alloys for dental application in various artificial solutions

The corrosion behavior of Ti-Nb dental alloy in artificial saliva with and without the addition of lactic acid and sodium fluoride was investigated by electrochemical techniques, with the commercial Titanium-molybdenum alloy (TMA) as a comparison. The chemical composition, microstructure and constitutional phase were characterized via energy dispersive spectrometry, optical microscope and X-ray diffraction, meanwhile the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements were carried out to study the corrosion resistance of experimental alloys, with the corroded surface being further characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the corrosion behavior of Ti-Nb alloy was similar to those TMA alloy samples in both artificial and acidified saliva solutions, whereas statistical analysis of the electrochemical impedance spectroscopy and polarization parameters showed Ti-Nb alloy exhibited better corrosion resistance in fluoridated saliva and fluoridated acidified saliva. SEM observation indicated that TMA alloy corroded heavily than Ti-Nb alloy in fluoride containing saliva. XPS surface analysis suggested that Nb₂O₅ played an important role in anti-corrosion from the attack of fluoride ion. Based on the above finding, Ti-Nb alloy is believed to be suitable for the usage in certain fluoride treated dental works with excellent corrosion resistance in fluoride-containing oral media.     

Co-based soft magnetic bulk glassy alloys optimized for glass-forming ability and plasticity

Co-based bulk glassy alloys (BGAs) have become more and more important because of their nearly zero magnetostriction and high giant magneto-impedance effect. Here, we report the improvement of glass-forming ability (GFA), soft-magnetic properties and plasticity by a small addition of Mo atoms in CoFeBSiNbMo BGAs. (Co_0.6Fe_0.4)₆₉ B _20.8Si_5.2Nb_5?x Mo _x ferromagnetic BGA cylindrical glassy rods were fabricated successfully with a diameter of 5 mm by conventional copper mould casting method. It reveals that the substitution of a small amount of Mo for Nb makes the composition to approach a eutectic point and effectively enhances the GFA of alloy. In addition to high GFA and superhigh strength, the compressive test shows that the Mo addition can improve the plasticity for the obtained BGAs. The combination of high GFA, excellent soft-magnetic properties and good plasticity demonstrated in our alloys is promising for the future applications as functional materials.     

Development of high Zr-containing Ti-based alloys with low Young's modulus for use in removable implants

This research focuses on the development of new titanium (Ti) alloys with a low Young's modulus for use in removable implants. In this study, Ti-30Zr alloy was selected as the base alloy, and the effect of Mo addition on the microstructures, Young's moduli, and tensile properties of Ti-30Zr-(0–8 wt.% Mo) alloys was investigated in this study to assess the mechanical compatibility of these alloys for biomedical applications. Further, the cytocompatibility of a part of the designed alloys was examined. The experimental results indicate that both the microstructures and the mechanical properties of the designed alloys are strongly affected by the Mo contents. The Ti-30Zr-(6, 7 wt.%) Mo alloys, located near the boundary of (β + ω)/β with a metastable structure, show a good combination of a low Young's modulus, high tensile strength, fairly large elongation. In addition, Ti–30Zr–7Mo alloy is highly cytocompatible.     

Gd-Dy-Fe-Co-Ge(Al)合金非晶形成能力及磁性能研究

利用铜模吸铸法和真空甩带法分别制得Gd-Dy-Fe-Co-Ge(Al)合金的铸锭和条带样品.利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)分析了合金的结构及热稳定性.并通过热重分析仪(TGA)、磁热效应测量仪研究了合金的居里温度及磁热效应.结果表明,Dy60Gd15Fe10Co10Ge5合金具有较好的非晶形成能力;用Al替换Dy元素,可以将合金的居里温度c调至室温附近;Dy47.7Gd15Fe10Co10Al12.3Ge5合金非晶条带样的磁热效应要优于铸态,在286K时,其铸态和非晶条带的绝热温变均达到峰值,分别为0.60、1.31K.s     

Nb添加对Ti基非晶合金腐蚀及力学性能的影响

为研究微量添加Nb元素对Ti_(40)Zr_(10)Cu_(34-x)Pd_(14)Sn_2Nb_x(x为原子数分数,x=0、1%、3%、5%)非晶合金的耐腐蚀性能及力学性能的影响,本文利用动态极化曲线,分析了在0.144 mol/L的NaCl溶液及0.2 mol/L的PBS溶液中非晶合金Ti_(40)Zr_(10)Cu_(34-x)Pd_(14)Sn_2Nb_x(x=0、1%、3%、5%)的电化学性能,并通过材料拉伸试验研究了非晶合金块状样品的室温压缩性能.结果表明:在0.144 mol/L的NaCl溶液中,非晶合金样品在阳极区出现了自发钝化的特征,钝化电流密度在10~(-7)～10~(-8) A/cm~2,钝化电流密度随着Nb的添加略有降低,且点蚀电位随Nb原子数分数的增加分别为200、340、400和490 mV,说明微量添加Nb元素能有效提高Ti基非晶合金的耐点蚀能力,即在0.144 mol/L的NaCl溶液中Ti基非晶合金的耐腐蚀性随着Nb含量的增加而增强;在0.2 mol/L的PBS溶液中,因磷酸根离子的缓蚀作用,Nb添加导致的成分变化对非晶合金的腐蚀行为影响不大;此外,添加了原子数分数为1%及3%Nb的非晶合金,其压缩强度及塑性变形能力变化不大,但添加5%Nb的非晶合金因较大体积分数纳米晶的存在导致其室温断裂强度及塑性变形能力有明显下降.     

Investigation of three-body wear behavior and hardness of experimental titanium alloys for dental applications in oral environment

The aim of this study was to investigate the three-body wear resistance and hardness of commercially pure titanium and titanium alloys containing zirconium and tantalum (cp-Ti, Ti-5Zr and Ti-5Ta). Each titanium test group, were subjected to wear tests under 10⁵ wear cycles, 50 N mechanical force, 2.0 Hz wear frequency, 6 mm diameter Al₂O₃ antagonist ball, 5 °C/55 °C thermal change conditions immersed in poppy seed slurry as third-body medium. The mean wear volume loss and depth of all test specimens after the three-body wear tests was determined with use non-contact 3D profilometer and also Vicker's hardness was measured. Wear area of microstructures were evaluated using scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. The hardness of Ti-5Zr material was significantly greater than the other alloy material and cp-Ti. However, for the test materials in this study considered, correlations between the three-body wear resistance and hardness were found to be insignificant. It was concluded, the three-body wear resistance of the alloy formed with the adding of zirconium and tantalum to the pure titanium is increased after wear tests.     

The corrosion and tarnish behavior of new palladium-indium system alloys

Emphasis on reduced costs has led to the greater use of economic alloys. Previous work has designed alloys with physical and mechanical properties similar to those of high gold alloys. Evaluation for the degree of corrosion and tarnish are to followed quantitatively by potentiodynamic and spectrophotometer analysis. In the view of the development in low nobility alloys, it is important that such testing be standardized to characterize the corrosion and tarnish properties of the compositions. But there are concerns with the long term chemical stability of these alloys, the resistance to corrosion and tarnish. Chemical stability is a complex problem involving alloy composition, nobility, microstructure and environment.     

The role of P content on the glass-forming ability and the magnetic properties of FeSiBPC amorphous alloys

Journal of Materials Science: Materials in Electronics - The effect of P content on the glass-forming ability (GFA) and soft magnetic properties of Fe83Si5?xB11PxC1 (x?=?0, 1, 2,...     

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.     

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.     

Effect of cold deformation on corrosion fatigue behavior of nickel-free high nitrogen austenitic stainless steel for coronary stent application

Due to the excellent mechanical properties, good corrosion resistance, high biocompatibility and nickel-free character, the high nitrogen nickel-free austenitic stainless steel (HNASS) becomes an ideally alternative material for coronary stents. Stent implantation works in harsh blood environment after a balloon dilatation, i.e., the material is used in a corrosive environment with a permanent deformation. The present study attempts to investigate effects of pre-straining on high-cycle fatigue behavior and corrosion fatigue behavior of HNASS in Hank’s solution and the relevant mechanism for coronary stents application. It is found that higher pre-straining on HNASS results in higher strength and maintains almost same corrosion resistance. Fatigue limit of 0% HNASS is 550 MPa, while corrosion fatigue limit is 475 MPa. And improvement in fatigue limit of 20% and 35% pre-strained HNASS is in comparison with the 0% HNASS, while corrosion would undermine the fatigue behavior of HNASS. In a suitable range, the pre-straining had a beneficial effect on corrosion fatigue strength of HNASS, such as nearly 300 MPa improved with 20% cold deformation. This result provides a good reference for predicting the life of HNASS stent and as well its design.     

Nd-induced honeycomb structure of intermetallic phase enhances the corrosion resistance of Mg alloys for bone implants

Mg-5.6Zn-0.5Zr alloy (ZK60) tends to degrade too rapid for orthopedic application, in spite of its natural degradation, suitable strength and good biocompatibility. In this study, Nd was alloyed with ZK60 via laser melting method to enhance its corrosion resistance. The microstructure features, mechanical properties and corrosion behaviors of ZK60-xNd (x?=?0, 1.8, 3.6, 5.4 wt.%) were investigated. Results showed that laser melted ZK60-xNd were composed of fine ɑ-Mg grains and intermetallic phases along grain boundaries. And the precipitated intermetallic phases experienced successive changes: divorced island-like MgZn phase?→?honeycomb-like T phase?→?coarsened and agglomerated W phase with Nd increasing. It was worth noting that ZK60-3.6Nd with honeycomb-like T phase exhibited an optimal corrosion behavior with a corrosion rate of 1.56?mm?year^?1. The improved corrosion behavior was ascribed to: (I) dense surface film caused by the formation of Nd₂O₃ hindered the invasion of immersion solution; (II) the three-dimensional honeycomb structure of intermetallic phases formed a tight barrier to restrain the propagation of corrosion. Moreover, ZK60-3.6Nd exhibited good biocompatibility. It was suggested that ZK60-3.6Nd was a preferable candidate for biodegradable bone implant.     

Reliability of Pd based dental alloys regarding to corrosion resistance and production processes

The knowledge of the relationship among chemical composition, microstructure, productive processes, functional properties, quality and price of the final product is an ever greater requirement for the firms producing dental alloys as well as for the dental laboratories making prosthesis. The present study deals with the evaluation of the corrosion resistance of high-Pd and Pd-Ag alloys by quantification of released ions following the recent European regulations suggested. Moreover the reliability of the alloys as far as concern their corrosion resistance was also investigated in relation to the different steps of alloy industrial production and restoration forming processes as well as after homogenization treatments followed by different cooling rate. The very complex microstructure of both alloys was greatly affected by the different casting conditions, deformation rate and thermal treatments used in alloy industrial production and prosthesis manufacturing. However the corrosion resistance of both alloys remained very good in all metallurgical states. The potentiodynamic tests allowed to distinguish among the structural conditions: the homogenization treatments, eliminating segregation inside the different phases, improved further the corrosion resistance of both alloys.     

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.     

Porous FeAl alloys via powder sintering:Phase transformation,microstructure and aqueous corrosion behavior

This study investigates the phase transformation and microstructure of porous FeAl parts sintered from elemental powder mixtures using in-situ neutron diffraction and in-situ thermal dilatometry.A single B2 structured FeAl phase was determined in the sintered FeAl alloy.The combined effects of the Kirk-endall porosity,transient liquid phase,and phase transformations associated with powder sintering all contribute to the swelling phenomenon of the final sintered part.The aqueous corrosion test indicates that the corrosion products include iron oxides in the porous FeAl parts.The accumulation of corrosion products blocks the pore channel and decreases pore size and permeability over the soaking time.     

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.     

Balancing benefits of strength,plasticity and glass-forming ability in Co-based metallic glasses

Development of advanced metals materials with ultrahigh strength,large plasticity and high thermosta-bility is one of the most attractive aims for materials researchers.Co-based bulk metallic glasses(BMGs)with the highest strength(up to 6 GPa)and special strength(up to 650 Nm/g)among all of metals mate-rials so far we known have received extensive attentions.In this paper,a family of Co-Ta-B-Si BMGs with high glass-transition temperature(above 870 K),large compressive plasticity(up to 6.4％)and high strength(above 5.5 GPa),and high glass-forming ability(the critical diameter,Dc:up to 4 mm)was devel-oped by accurately tuning metalloid element contents of Si and B in the parental alloy of Co55Ta10B35.The changes of glass formation and plasticity caused by the adjustment of the constituent metalloid elements were evaluated by the combination of experimental and calculated results.The reason for the significant improvement of plastic deformation is revealed by the analysis of the self-organization behaviors of high-density shear bands.     

Mechanical characterization and corrosion behavior of newly designed Sn and Y added AZ91 alloy

This paper deals the effect of Sn and Y additions on the microstructure, mechanical and corrosion properties of AZ91 alloy. It is found that by the addition of Sn, the formation and growth of discontinuous precipitate get suppressed and new intermetallic Mg₂Sn phase is formed. In the case of Y addition together with Sn, the grain size gets refined, the volume of Mg₁₇Al₁₂ gets decreased and new intermetallic Al₂Y phase is observed. Improved room and high temperature tensile properties are obtained in as-cast and aged Sn and Y added AZ91 alloy. However, maximum properties are obtained for the alloy having combined addition of 0.5 wt.% Sn and 0.9 wt.% Y. Improved corrosion resistance is also noticed with the addition of Sn and Y elements.