Surface Of AZ31 Magnesium Alloy Research Articles

Bio-inspired immobilization of strontium substituted hydroxyapatite nanocrystals and alendronate on the surface of AZ31 magnesium alloy for osteoporotic fracture repair

Osteoporosis is a significant public health problem associated with increased fracture risk. Magnesium (Mg) alloys are promising biodegradable implant materials for osteoporotic bone fracture repair due to their mechanical compatibility and biological safety. However, the degradation rate of Mg alloy does not match the healing rate of the fracture and the growth rate of new bone tissues. In order to treat and prevent osteoporosis, enhance peri-implant bone formation, inhibit bone resorption and slow down the degradation of Mg alloy, herein, we developed a novel bio-inspired therapeutic coating strategy by co-immobilizing strontium (Sr) substituted hydroxyapatite (Sr-HA) nanocrystals and bisphosphonate (BP) alendronate on the surface of AZ31 Mg alloy with the aid of polydopamine and carboxymethyl chitosan (CMCS). Such novel functionalized coating can not only improve the corrosion resistance of Mg alloy but also stimulate the proliferation and differentiation of osteoblast cells due to the sustained release of ALN and Sr ions from Sr-HA nanocrystals. The present coating strategy provides deep insights into clinical repair of osteoporosis-associated fractures and can potentially be extended to design of many other orthopedic devices.

Synthesis and properties of hydroxyapatite-containing coating on AZ31 magnesium alloy by micro-arc oxidation

In this study, hydroxyapatite-containing coatings were prepared by microarc oxidation on AZ31 magnesium alloy surface to improve its biodegradation performance. Five applied voltages were chosen to prepare the MAO coatings. The results demonstrate that the number of micropores in the films increases but their dimensions decrease after higher voltage is applied. As the surface roughness of the MAO coatings increases with the applied voltage, the wettability of the coatings improves continuously. The MAO coatings were mainly composed of magnesium oxide (MgO) and hydroxyapatite. The amount of hydroxyapatite phase increased with increasing voltage that was applied. The bonding strength became slightly weaker after a higher voltage was applied. But the bonding strengths of all the coatings were consistently higher than 37MPa, which met the requirement of implant biomaterials. All coatings exhibited higher corrosion resistances and lower hydrogen evolution rate than the bare AZ31 Mg substrate, implying that the degradation rate of the AZ31 Mg alloy was enhanced by the hydroxyapatite-containing coatings. The results indicate that the present treatment of applying hydroxyapatite-containing coatings is a promising technique for the degradable Mg-based biomaterials for orthopedic applications.

Deposition and Characterization of Electrophoretic Paint on AZ31 Magnesium Alloy

In this study, electrophoretic paint (E-paint) was deposited on the knife-abraded surface of AZ31 magnesium alloy (AZ31), and its adhesion and corrosion resistance were examined by tape peel-test and salt spray test, respectively. E-paint started to deposit on AZ31 Mg alloy after an inductance time and pores were found in the E-paint layer which is ascribed to hydrogen bubbles generated on the surface during the painting process. The pores disappeared after curing for 15 min at <TEX>$160^{\circ}C$</TEX>. The E-paint on AZ31 exhibited good adhesion after immersion in deionized water for 500 h at <TEX>$40^{\circ}C$</TEX>. The E-paint sample without scratch showed no corrosion after 1500 h of salt spray test. However, on the scratched sample, blisters were visible adjacent to the scratched sites after 500 h of salt spray test.

Study the Influence of Surface Treatment Technology to AZ31 Property Change

Magnesium alloy which is one of the least light density (about1.7g/cm3) composites material on the ground for trade business, this material has better strength ratio of room temperature, high strength and rigidity, with good vibration attenuation, better damping, and good heat conduction,resistant radiation, don’t produce spark when friction, good ductility, better cutting machine and formed possibility, may be welded, adhesives, and have good chemical stability to Alkali, kerosene, gasoline, mineral oil and dry atmosphere, With no magnetic and electromagnetic shielding properties, Magnesium alloy products easy to recycle and no pollution to environment etc. Known as in twenty-first century the "green engineering materials”, In order to improve the use range of alloy,it need for improved performance of AZ31 magnesium alloy, AZ31 magnesium alloy surface modification technology to solve the main problems is to reduce the cost and environmental issues of a single technology, There is a wide prospect for the application of compound modification.

Fabrication and characterization of a hydroxyapatite–methylcellulose composite coating on the surface of AZ31 magnesium alloy

Magnesium alloys are attracting attention as materials for use in biological applications. In this work, Ca(OH)2 and Ca(H2PO4)2·H2O are used as raw materials, and methylcellulose is used as an additive, to prepare a hydroxyapatite–methylcellulose composite coating on the surface of AZ31 magnesium alloy using a sol–gel technique. Phase analysis, a surface morphology study, and cross-section and microstructure characterization of the hydroxyapatite–methylcellulose composite coating are presented. Potentiodynamic polarization curves and corrosion morphologies of the coating are also presented. The results indicate that the thickness of the hydroxyapatite–methylcellulose composite coating is approximately 60μm and the composite coating could improve the biodegradation property of AZ31 magnesium alloy effectively.

Investigation of the Surface Modification on Biomedical Magnesium Alloy

In this work, the green chemistry conversion coating on AZ31 magnesium alloy surface was made and studied by means of Ce (SO4)2·2(NH4)2SO4·4H2O and MnSO4 as inhibitor, H2O2 as oxidant, NaCl as accelerator, CH3COOH as stabilizer. The coating was evaluated in simulated body fluid (SBF) with pH=7.4 at 37°C by using electrochemical impedance spectroscopy (EIS). The results show the conversion coating resistance, for the untreated or treated alloy, is 0.75 kΩ·cm2 and 3.28 kΩ·cm2 respectively. It indicates the conversion coating treated surface presents better corrosion behaviour in SBF than the original material surface. The morphologies and composition the coating were examined by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) respectively. The result indicates that the Ce-Mn conversion coating was made on magnesium alloy surface. Biocompatibility of conversion coating was investigated by use of cell toxicity. Cell culture has shown that the magnesium alloy has good cytocompatibility.

Effect of Schiff base as corrosion inhibitor on AZ31 magnesium alloy in hydrochloric acid solution

Schiff base derived from the condensation reaction of analar grade 1-amino-2-naphthol 4-sulphonic acid with cinnamaldehyde was prepared under microwave condition. The Schiff base was analysed by infrared spectroscopy. This Schiff base as a corrosion inhibitor of AZ31 magnesium alloy in 0.05 mol/L HCl solution was studied. The inhibition effect of the Schiff base compound (4Z)-4-(3-phenyl allylidene amino)-3-hydroxy naphthalene-1-sulfonic acid (AC) on AZ31 magnesium alloy corrosion was studied using mass loss, potentiodynamic polarization technique, electrochemical impedance spectroscopy methods. The potentiodynamic polarization curve shows that Schiff base AC inhibits both anodic and cathodic reactions at all concentration, which indicates it is a mixed type inhibitor. EIS results indicate that as the additive concentration is increased, the polarization resistance increases whereas double-layer capacitance decreases. The adsorption of AC on the AZ31 magnesium alloy surface in 0.05 mol/L HCl obeys the Langmuir adsorption isotherm.

Effects of an overlapping multi-pass friction stir process and rapid cooling on the mechanical properties and microstructure of AZ31 magnesium alloy

Applications for magnesium as the lightest structural metal are increasing; however, its low ductility at room temperature could be considered a limitation. The friction stir process (FSP) is a solid state process that can overcome this limitation by producing a fine-grained material and uniform texture. This study used overlapping passes FSP to create a fine-grained area on the surface of AZ31 magnesium alloy. Rapid cooling was employed during the process to eliminate the thermal effects of successive passes. Two different modes of overlap were created. In the first mode, the surface of the sample was FSPed overlapping in one direction. In the second mode, the first overlapped surface of the sample was overlapped again in a direction perpendicular to the primary process. The results showed that mechanical strength in the process direction increased for both modes. Elongation was greater for the first mode than that of the raw material and, for the second mode, was less than for the raw material. In the direction perpendicular to the process, both the mechanical strength and ductility of the material were less than those of the raw material. The particle distribution in the second mode was more uniform than that for the first mode.

Plasma electrolytic oxidation coatings in KOH electrolyte and its discharge characteristics

The ceramic coatings on the surface of AZ31 magnesium alloy were prepared via plasma electrolytic oxidation (PEO) of potassium hydroxide electrolyte. The discharge characteristics and the composition of the coatings were studied. The state evolution of the substrate surface during the PEO process were detected by optical emission spectroscopy (OES) and a high speed camera. The results of OES show that in the anodic oxidation stage, light emission could be attributed to electroluminescence because of the “flaws” of the dielectric barrier layer. The movement of the spectral peak also occurred at the anodic oxidation stage because of different “flaws” in the dielectric barrier layer. At the transition stage, light emission could be attributed to the ionization species present in the bubbles. At the discharge stage, the main active plasma species in the plasma field were Na, K, Mg, and O2+, which resulted in the light emitting. The coatings were mainly composed of MgO and Mg(OH)2.

Synthesis and properties of CaTiO3-containing coating on AZ31 magnesium alloy by micro-arc oxidation

Magnesium and its alloys are thought as biodegradable implant materials due to their attractive biological properties. But the application of magnesium is still hampered by their poor corrosion resistance and inert bioactivity in physiological circumstances. In this article, a CaTiO3-containing coating was deposited on AZ31 magnesium alloy surface by micro-arc oxidation (MAO). The microstructure and composition were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The corrosion behavior and apatite-forming ability were studied by electrochemical tests and immersing in simulated body fluids (SBF). The results show that the MAO coating significantly improves the corrosion resistance of AZ31 magnesium alloy and enhances the apatite formation ability.

The effect of NaHCO3 treatment time on the corrosion resistance of commercial magnesium alloys AZ31 and AZ61 in 0.6 M NaCl solution

This paper studies the chemical composition and structure of the conversion coatings formed during immersion on saturated aqueous NaHCO3 solution treatment on the surface of as-received commercial AZ31 and AZ61 magnesium alloys with a view to a better understanding of their protective properties. The great uniformity and the significant increase in the amount of aluminium oxides and hydroxides observed on the surface of the conversion coating of the AZ61 alloy after 10 or 60min of treatment (about 30% higher Al atomic contents) seems to improve the corrosion resistance.

Phosphate film free of chromate, fluoride and nitrite on AZ31 magnesium alloy and its corrosion resistance

A phosphate solution free of chromate, fluoride and nitrite was prepared and an environment-friendly film was obtained on AZ31 magnesium alloy surface via the chemical deposition method. The morphology, composition, phase structure and its corrosion resistance were studied. The effects of film-forming temperature and free acid on corrosion resistance, microstructure and electrochemical behavior of the film were discussed. The results indicate that the corrosion resistance of AZ31 with the phosphate film was better than blank AZ31 substrate, which was most attributed to the great inhibitive action on the anodic dissolution and cathodic hydrogen evolution of the film.

High-compactness coating grown by plasma electrolytic oxidation on AZ31 magnesium alloy in the solution of silicate–borax

A ceramic coating was formed on the surface of AZ31 magnesium alloy by plasma electrolytic oxidation (PEO) in the silicate solution with and without borax doped. The composition, morphology, elements and roughness as well as mechanical property of the coating were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and reciprocal-sliding tribometer. The results show that the PEO coating is mainly composed of magnesia. When using borax dope, boron element is permeating into the coating and the boron containing phase exist in the form of amorphous. In addition, the microhardness and compactness of the PEO coating are improved significantly due to doped borax.

Corrosion resistance and mechanical property of AZ31 magnesium alloy by N/Ti duplex ion implantation

N/Ti duplex ion implantation was conducted on AZ31 magnesium alloy surface by metal vapor vacuum arc (MEVVA) ion source to improve its corrosion resistance and mechanical property. Auger electron spectrum (AES), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to characterize the elemental concentration-depth profiles and phase composition of the modified layer. The anti-corrosion performance of treated samples was evaluated using potentiodynamic polarization system and scanning electronic microscope (SEM). The surface hardness of ion implantation samples were measured by hardness tester. XRD analysis shows that Mg, MgO, Ti, TiO2 and TiN phases exist in the surface modification layer. AES result indicates that the surface layer thick is about 200nm; the ion dose and thickness of the implanted layer increase with the implantation voltage and treatment time. The depth profile of implanted N+Ti in AZ31 magnesium alloys is similar to Gauss distribution, and the maximum concentration up to 66at.%. The hardness of treated sample is 94.5HV0.01, increases by 50.7%. Compared with the bare substrate, the corrosion potential Ecorr of N/Ti duplex ion implantation coupon increases by 600mV, the corrosion current density icorr decreases by two orders of magnitude, and the polarization resistance increases by 66.4 times in a 0.56M NaCl solution. The corrosion resistance can be slightly improved by low implantation voltage. In addition, too high implantation voltage or too long treatment time have a negative influence on the corrosion resistance. The corrosion resistance of AZ31 magnesium alloy can be effectively improved by nitrogen and titanium duplex ion implantation.

501 AZ31Mg合金へのAl合金の積層による機械的特性改善

To improve mechanical properties of magnesium alloys, laminated material coated with aluminum alloys on the surface of AZ31 magnesium alloy using the inserted titanium foil has been developed by solid-phase diffusion bonding. After vacuum hot pressing for preforming, laminates materials were applied hot rolling. The bonding strength is influenced strongly by the bonding temperature and applied stress, and the best bonding condition were studied. The mechanical properties of laminates materials were investigated by tensile test and fracture toughness test. As results of these tests, developed laminate composite materials were confirmed to improve plastic formability property and mechanical properties.

Characteristics of TiN and NCD Layers Deposited on Magnesium Alloys

Magnesium alloys have been widely used in numerous branches of industry in which reduced mass is of great importance. These alloys are used in aeronautic, astronautic, electronic and sporting goods industries etc. The growing significance of the material magnesium is also closely associated with the progressive development in the field of automotive lightweight construction. The most captivating advantages of magnesium alloys include: the high ratio of mechanical durability to their mass, an excellent heat conductivity, low heat expansion, good casting properties, high functional integrity enabling manufacturing of goods with near-net-shape and good machinability. Magnesium alloys display also some disadvantages, like first of all, the high susceptibility to corrosion, low wear resistance and reduced durability. These disadvantages considerably limit applications of magnesium alloys in industry. The presented work demonstrates the method of deposition of special TiN (Titanium Nitride) and NCD (Nanocrystalline Diamond) layers on the surface of AZ31 magnesium alloys which eliminates these disadvantages. Besides, such layers play both the protective and decorative roles. TiN layers have been deposited by Plasma Activated Physical Vapour Deposition method (PAPVD) in ECAM-France and NCD layers by Plasma Activated Chemical Vapour Deposition method (PACVD) in the Institute of Material Science at the Technical University of Lodz-Poland. This paper shows the method of identification of manufactured layers and investigation results of tribological properties of these layers. Also samples preparation using grinding and polishing method before manufacturing of protective TiN and NCD layers has been depicted.

Corrosion behaviors in physiological solution of cerium conversion coatings on AZ31 magnesium alloy

In this paper, a non-toxic Ce-based conversion coating was obtained on the surface of bio-medical AZ31 magnesium alloys. The micro-morphology of the coating prepared with optimal technical parameters and immersed in physiological solution (Hank's solution) in different time was observed by scanning electron microscopy (SEM), composition of the cerium conversion coating and corrosion products in Hank's solution were characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), respectively. In addition, the corrosion property in Hank's solution was studied by electrochemical experiment and immersion test. The results show that the dense Ce-based conversion coating is obtained on the surface of AZ31 magnesium alloys in optimal technical parameters and the conversion coating consists of a mass of trivalent and tetravalent cerium oxides. The cerium conversion coating can provide obvious protection of magnesium alloys and can effectively reduce the degradation speed in Hank's solution. Also the degradation products have little influence on human body.

Surface Treatment to Provide a Metallic Luster to AZ31 Magnesium Alloy

To form a metallic luster on AZ31 magnesium alloy, it is necessary to optimize the surface morphology since the surface roughness affects the specular reflection of visible light, and the surface structure such as the film thickness and properties must be optimized so that light is not absorbed. We conducted experiments to analyze the relationship between surface roughness and specular reflection, and determined the range required to produce metallic luster. The ratio of the root mean square roughnessto the wavelength of incident lightwas 0-0.067, and the ratio of the specular reflectivity R of the specimens to the specular reflectivity of a smooth surface R0 was 0.54-1.0. The thickness of film to form a metallic luster was theoretically analyzed and found to be about 100 nm or less. The authors developed an optimum acid aqueous solution for treating the surface to form a metallic luster on the surface of AZ31 magnesium alloy. This treatment satisfied the range required to form a metallic luster identified theoretically, and formed a film with a stable structure that maintained its metallic luster. The treatment maintained the geometrical patterns such as the hair-line and blast finishing of several hundred nm or more. A sufficiently high-quality surface for exterior parts was obtained by improving the process, and the process was industrialized. (doi:10.2320/matertrans.MC201010)

Acid aqueous solution treatment method in AZ31 magnesium alloy

In order to impart metallic luster to AZ31 magnesium alloy, the conditions of surface treatment were optimized, and the formative mechanism of metallic luster on the surface was inferred from the results of surface analysis. The target of this study was the surface of AZ31 magnesium alloy that was polished by emery paper (#2000) . When the optimal acid aqueous solution treatment was applied, more than 60% of the magnesium in the film was oxidized. In addition, the thickness of the film was about 55 nm. It was confirmed that hydrogen generation was inhibited under the optimized surface treatment conditions. This optimization was performed by examining oxidant addition and the temperature of the acid aqueous solution, and metallic luster was successfully imparted to the alloy. In the optimal acid aqueous solution treatment, it was found that the reaction rate of magnesium oxide formation was faster than that of the dissolution of magnesium from the film composed of magnesium oxide on the surface. For surface treatment conditions in which a dull surface was obtained, it is speculated that the surface became rough due to the generation of hydrogen.

Adsorption and Corrosion Inhibition Behavior of Sodium Dodecylbenzenesulfonate on AZ31 Magnesium Alloy

Electrochemical impedance spectroscopy (EIS) and polarization curves were used to study the adsorption and corrosion inhibition of sodium dodecylbenzenesulfonate (SDBS) on AZ31 magnesium alloy in 3.5% (w, mass fraction) NaCl corrosive medium. Results showed that SDBS strongly inhibited the corrosion of AZ31 magnesium alloy in NaCl medium. The inhibition efficiency of 0.008 mol·L-1 SDBS was more than 90%. Increasing temperature did not increase the inhibition efficiency. Physical adsorption of SDBS at the AZ31 magnesium alloy surface mainly occurred. The adsorption process was spontaneous and exothermic and the entropy increased, which obeyed the Langmuir isotherm. SDBS is a mixed-type inhibitor and mainly inhibits the anodic dissolution reaction of AZ31 magnesium alloy.