Research and Application of Platinum/tantalum Composite Anode for Cathodic Protection

This paper introduces the research status and present situation of application of Pt/Ta composite anode materials for cathodic protection in China. It also introduces the corrosion resistance, bending properties and electrochemical performance in seawater and freshwater of the Pt/Ta composite anode materials for cathodic protection. It points out that compared with other platinum composite anodes, the Pt/Ta composite anode has the advantage of small volume, light weight, big drainage rate, long service life, it possesses superiority to be used in the confluence environment of sea water and fresh water and in the medium condition of resistivity changes at all times.

An intermediate poly-dopamine layer for alginate coating on high-purity magnesium to achieve corrosion mitigation

Although magnesium(Mg)and its alloys are proposed as the next generation orthopedics transplanted materials,their clinical applications are limited by the fast degradation.To reduce the degradation rate,a strong adhesion poly-dopamine(PDA)layer was introduced as an intermediate layer for the subsequent alginate(ALG)spin-coating on high-purity Mg.The surface morphology and chemical composition were detected by scanning electron microscope,energy disperse spectroscopy,and Fourier transform infrared spectroscopy.The corrosion resistances of all samples were evaluated by electrochemical and 10-day immersion tests in Hanks’balanced salt solution.Our results suggest that the thickness of the fabricated PDA/ALG composite coating is 8.58±0.65μm,and the intermediate PDA layer evidently enhances the adhesion between the substrate and ALG coating.The corrosion current density of Mg coated with the PDA/ALG composite coating decreases more than 10 times compared to that of the Mg substrate,and the charge transfer resistance is 12 times bigger than that of the bare Mg,which indicates the improved corrosion resistance.Moreover,the mechanism of corrosion protection of the composite coating is also discussed.

Fracture criterion for predicting surface cracking of Ti40 alloy in hot forming processes

Hot compression tests were conducted on Ti40 burn resistant titanium alloy in the temperature range of 900-1 100 ℃ and strain rate range of 0.01-10 s-1 to investigate its fracture behavior and critical fracture conditions in hot forming. It was observed that the failure of Ti40 alloy is attributed to longitudinal surface cracking due to severe oxidation of element V and the secondary tensile stresses. The critical fracture strain increases with increasing temperature and decreasing strain rate. From these observations and parallel FEM simulations,it was concluded that the critical fracture strain is a function of a single argument Zener-Hollomon parameter,and there is a linear relationship between them. An Oyane criterion successfully predicted the location of crack initiation. The critical fracture values also exhibit a liner relationship with lnZ. Based on these results,a new fracture criterion of Ti40 alloy based on Zener-Hollomon parameter was established.

Relationship among forging technology, structure and properties of TC21 alloy bars

As candidate of structural material for advanced domestic aircraft, a new high strength and toughness titanium alloy TC21 was studied focusing on forging technology and microstructure as well as mechanical properties. Two specification ingots and bars were adopted. The results show that basket-weave microstructure is obtained in bars produced by beta finish-forging method; while duplex or tri-modal microstructure appears in bars manufactured by near-beta forging technology. Essential reason affecting structure characteristics is the difference in forging temperature and deformation amount. Variation in lamellar spacing results in fluctuation of properties corresponding to basket-weave microstructure; however, ideal matching of properties can be reached by near-beta forging.

Morphology and Crystallinity-controlled Synthesis of Manganese Cobalt Oxide/Manganese Dioxides Hierarchical Nanostructures for High-Performance Supercapacitors

We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.

Advances in graphene reinforced metal matrix nanocomposites:Mechanisms,processing,modelling,properties and applications

Graphene has been extensively explored to enhance functional and mechanical properties of metalmatrix nanocomposites for wide-range applications due to their superior mechanical,electrical and thermal properties.This article discusses recent advances of key mechanisms,synthesis,manufacture,modelling and applications of graphene metal matrix nanocomposites.The main strengthening mechanisms include load transfer,Orowan cycle,thermal mismatch,and refinement strengthening.Synthesis technologies are discussed including some conventional methods(such as liquid metallurgy,powdermetallurgy,thermal spraying and deposition technology)and some advanced processing methods(such as molecular-level mixing and friction stir processing).Analytical modelling(including phenomenological models,semi-empirical models,homogenization models,and self-consistent model)and numerical simulations(including finite elements method,finite difference method,and boundary element method)have been discussed for understanding the interface bonding and performance characteristics between graphene and different metal matrices(Al,Cu,Mg,Ni).Key challenges in applying graphene as a reinforcing component for the metal matrix composites and the potential solutions as well as prospectives of future development and opportunities are highlighted.

Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti2Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti2Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which along grain boundaries during semisolid processing. is attributed to the presence of precipitate-free zones formed

Development of a database system for operational use in the selection of titanium alloys

The selection of titanium alloys has become a complex decision-making task due to the growing number of creation and utilization for titanium alloys,with each having its own characteristics,advantages,and limitations.In choosing the most appropriate titanium alloys,it is very essential to offer a reasonable and intelligent service for technical engineers.One possible solution of this problem is to develop a database system（DS） to help retrieve rational proposals from different databases and information sources and analyze them to provide useful and explicit information.For this purpose,a design strategy of the fuzzy set theory is proposed,and a distributed database system is developed.Through ranking of the candidate titanium alloys,the most suitable material is determined.It is found that the selection results are in good agreement with the practical situation.

Microstructures and mechanical properties of a new titanium alloy for surgical implant application

A new titanium alloy Ti12.5Zr2.5Nb2.5Ta（TZNT） for surgical implant application was synthesized and fully annealed at 700℃for 45 min.The microstructure and the mechanical properties such as tensile properties and fatigue properties were investigated.The results show that TZNT mainly consists of a lot of lamellaα-phase clusters with different orientations distributed in the originalβ-phase grain boundaries and a small amount ofβphases between the lamella a phases.The alloy exhibits better ductility,lower modulus of elasticity,and lower admission strain in comparison with Ti6A14V and Ti6A17Nb,indicating that it has better biomechanical compatibility with human bones.The fatigue limit of TZNT is 333 MPa,at which the specimen has not failed at 10^7 cycles.A large number of striations present in the stable fatigue crack propagation area,and many dimples in the fast fatigue crack propagation area are observed,indicating the ductile fracture of the new alloy.

Grain boundary characteristics and tensile properties of Ti14 alloy after semi-solid deformation

The microstructure and room-temperature tensile properties of Ti14,a new α＋Ti2Cu alloy,were investigated after conventional forging at 950°C and semi-solid forging at 1000 and 1050°C,respectively.Results show that coarse grains and grain boundaries are obtained in the semi-solid alloys.The coarse grain boundaries are attributed to Ti2Cu phase precipitations occurred on the grain boundaries during the solidification.It is found that more Ti2Cu phase precipitates on the grain boundaries at a higher semi-solid forging temperature,which forms precipitated zones and coarsens the grain boundaries.Tensile tests exhibit high strength and low ductility for the semi-solid forged alloys,especially after forging at 1000°C.Fracture analysis reveals the evidence of ductile failure mechanisms for the conventional forged alloy and cleavage fracture mechanisms for the alloy after semi-solid forging at 1050°C.

Hot deformation behavior and constitutive equations of titanium alloy Ti26

Samples of Ti26(Ti-V-Sn-Cr-Al-Zr-Nb) alloy were compressed on the Gleeble-1500 heat stimulation machine. The compression test was carried out at 900-1 150 ℃ and strain rates from 0.001 s-1 to 10 s-1. Flow stress data at various temperatures and strain rate were obtained;and the compressive true stress vs. true strain curves were measured and studied. The deformation activation energy was calculated. The results show that the flow stress of Ti26 alloy decreases with the increase of temperature and the decrease of strain rate,and the deformation activation energy is 278.11 kJ/mol in β phase region. The flow stress curves and deformation activation energy reveal that the main softening mechanism is dynamic recovery in β phase region. Constitutive equations were formulated to describe the temperature dependence of the flow stress over a wide range of strain rates.

Effect of deformation processing parameter on microscopic structure of Ti14 alloy under semi-solid

Hot compressive deformation test of Ti-Al-Cu-Si alloy was performed on Gleeble-3500 hot-Simulator over the range of deformation temperature from 1 000 to 1 300 ℃,strain rate from 0.005 s-1 to 5 s-1,deformation degree from 40% to 70%,and samples of d 8 mm×15 mm were used. Change rules of microstructure were mainly studied. The results show that deformation temperature directly influences the nucleation growth and globurizing of grain,and with the temperature rising,the diameter of grain increases,the grain boundary widens. The effect of deformation degree on microstructure varies with deformation temperature. Equivalent diameter of grains shows a trend of falling before elevation with strain rate increasing and temperature rising.

Endoscopic magnetic compression stricturoplasty for congenital esophageal stenosis:A case report

BACKGROUND Congenital esophageal stenosis(CES)is a rare malformation of the digestive tract.Endoscopic dilation and thoracotomy have been the main treatments for CES.However,there is no well-defined management protocol.Magnetic compression stricturoplasty(MCS)has been used in refractory esophageal stricture in children after esophageal atresia.CASE SUMMARY We describe the first case of MCS for CES in one female child patient.The child(aged 3 years and 1 mo)was admitted due to frequent vomiting and choking after eating complementary food since 7 mo old.Esophagography and gastroendoscopy showed that there was stenosis in the lower esophagus,suggesting a diagnosis of CES.The patient did not receive any treatment for esophageal stricture including surgery or endoscopic dilation procedures before MCS.MCS procedure was smoothly conducted without complications.At 24 mo after MCS,durable esophageal patency without dysphagia was achieved.CONCLUSION MCS may serve as an alternative and efficient method for patients with CES.

Phase Evolution Study and Optimization of the Heat Treatment Process for High Current Capacity Bi-2223 Tapes

Powder in tube process（PIT） was adopted for the fabrication of single filament Bi-2223 tapes, and a heat treatment process including the first heat treatment（HT1）, intermediate rolling（IR）, and second heat treatment（HT2） was performed. The phase evolution mechanism and microstructure changes during these heat treatment processes were systematically discussed. The influences of HT1 parameters on the phase evolution process of Bi-2223 tapes were discussed. With the optimized HT1 process, a proper Bi-2223 content of about 90% was achieved. HT2 process was also optimized by adding a post annealing process. An obvious increase of current capacity was obtained due to the enhancement of intergrain connections. Single filament Bi-2223 tapes with the critical current of Ic-90 A were fabricated with the optimized sintering process.

Current research situation of titaniumalloys in China

Titanium and its alloys possess excellent comprehensive properties, and they are widely used in many fields. China pays great attentions to the research on new titanium alloys. This paper mainly reviews the research on new Ti alloys in China, for example, high strength and high toughness Ti alloys, burn resistant Ti alloys, high temperature Ti alloys, low cost Ti alloys and so on. New basic theories on Ti alloys developed in China in recent years are also reviewed.

In-situ SEM Observation of Monotonic and Cyclic Deformed Structure in Ti-2A1-2.5Zr Alloy

The SEM observation in situ of monotonic and cyclic deformed structure in Ti-ZA1-2.5Zr alloy was performed. The regularity of slippage, crack nucleation, propagation and the typical dislocation configuration were also investigated. The twin and twist play an important role in maintaining homogeneous deformation in the final plastic deformation stage.

Corrosion behaviors of a new titanium alloy TZNT for surgical implant application in Ringer’s solution

A new near α-titanium alloy Ti12.5Zr2.5Nb2.5Ta （TZNT） for surgical implants was designed. The potentiodynamic technique was performed to investigate the corrosion behaviors of TZNT in Ringer＇s solution, and Ti6A14V, Ti6Al7Nb, and TA2 were taken as comparison. The structure of the passive film was analyzed using an X-ray photoelectron spectrometer （XPS）. The results indicate that TZNT possesses better corrosion resistance, when compared with Ti6A14V, Ti6A17Nb, and TA2. The passive film formed on the TZNT surface is composed of oxides, such as TiO2, ZrO2, Nb2O5, and Ta2O5. The elements Zr and Ta are rich, whereas Ti and Nb are poor in the passive film. The addition of Zr, Nb, and Ta with relatively low electrochemical reaction potentials can reduce the anode activity and improve passive properties. Other than that, oxides such as ZrO2, Nb2O5, and Ta2O5 with the nobler equilibrium constants make the passive film more stable.

Study on Numerical Simulation for Control of Winding Process of Thin Wall Spiral Tube

Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separation of hydrogen in the winding process, this article analyzed the reasons for above phenomena, established a numerical simulation model of winding process of above tube, using elastic-plastic Finite Element method analyzed the max. tensile stress and max. compression stress and their locations, thereby provides a theory base for the control of working forming course of thin wall spiral tube.

Limit of structure refinement for 7075 aluminum alloy at elevated temperature by hot deformation

Performance of commercial alloys can be improved greatly by severe plastic deformation, which refines grain of metals to several micrometer or sub micrometer order. During severe plastic deformation, the final size of grain structure depends on the following factors: strain rate, total strain, deformation temperature and so on. Under a certain condition, structure cannot be infinitely refined, which means that the size of grain has a limit with the increase of total strain. Under conventional hot deformation temperature, the grain size of 7075 aluminum alloy can be refined to 12 μm, and it will not become smaller with the increase of total strain, that is to say, the limit of grain refinement is about 1 μm.