Mg alloy surface alloying layer fabricated through evaporative pattern casting technology

The influencing factors of surface alloying layer by evaporative pattern casting technology were investigated.A certain thickness alloying layer was formed on the surface of Mg-alloy matrix when the pouring temperature was 780°C with different vacuum degree and alloying powder size.The surface layer microstructure,micro area composition of the new phase formed on the matrix and the composition characteristics on the surface layer were examined by SEM and element scanning.The results show that the content of aluminum increases greatly on the surface layer.The micro-hardness of alloyed layer has a more obvious increase compared with that of the matrix.The size of alloying element and the vacuum degree are the key factors influencing the alloying layer,with the increase of element powder size from 0.074 to 0.15 mm and vacuum degree from 0.04 to 0.06 MPa,the surface alloying effect becomes better.

Effects of reflowing temperature and time on alloy layer of tinplate and its electrochemical behavior in 3.5%NaCl solution

Effects of reflowing temperature and time on the alloy layer of tinplate and its electrochemical behavior in 3.5%NaCl solution were investigated by electrochemical measurements and surface characterization.It is found that the amount of alloy layer increases with the increase of reflowing temperature and time.Then the corrosion potential of detinned tinplate shifts positively and the corrosion rate decreases.After being coupled with tin,the detinned tinplate acts as cathode and tin acts as anode initially.However,after being exposed for some time,the potential shifts of both detinned tinplate and tin reverse the polarity of the coupling system.The galvanic current density decreases with the increase of reflowing temperature and time.

Fast ion diffusion alloy layer facilitating 3D mesh substrate for dendrite-free zinc-ion hybrid capacitors

Although aqueous zinc ion hybrid capacitors have advantageous integration of batteries and supercapacitors,they still suffer from the inherent problems of dendrite growth and interfacial side reactions on Zn anodes.Herein,a universal fast zinc-ion diffusion layer on a three-dimensional(3 D)mesh structure model is demonstrated to effectively improve Zn plating/stripping reversibility.The fast ion diffusion alloy layer accelerates the Zn^(2+)migration in an orderly manner to homogenize Zn^(2+)flux and overcomes the defects of the commercial mesh substrate,effectively avoiding dendrite growth and side reactions.Consequently,the proof-of-concept silver-zinc alloy modified stainless steel mesh delivers superb reversibility with the high coulombic efficiency over 99.4%at 4 mA cm^(-2)after 1600 cycles and excellent reliability of over 830 h at 1 mA cm^(-2),Its feasibility is also evidenced in commercial zinc ion hybrid capacitors with activated carbon as the cathode.This work enriches the fundamental comprehension of fast zinc-ion diffusion layer combined with a 3 D substrate on the Zn deposition and opens a universal approach to design advanced host for Zn electrodes in zinc ion hybrid capacitors.

Generation reason and corrosion characteristicof cavity of tinplate alloy layer

The surface morphology of alloy layer of tinplate was studied by means of scanning electron microscopy. By using the layer on layer debonding technology of glow discharge spectrum, the contents of C and O at the boundary of alloy layer and black plate were analyzed. And the corrosion characteristic of cavity of tinplate alloy layer was studied on-line and in-situ by means of electrochemical atomic force microscope. The corrosion depth of cavity of alloy layer in-situ after different corrosion time was measured. The results show that the cavity of alloy layer is a critical factor causing rapid decline of corrosion resistance of tinplate, and the formation of cavity of alloy layer is due to incorrect pretreatment of black plate before electrotinning. The cavity of alloy layer is the internal factor causing pitting corrosion of tinplate when the tinplate is applied to food packaging material. And the dynamic equation of pitting corrosion generated in the cavity of alloy layer conforms to logarithm law.

SOLUTION TO THE STRESS DISTRIBUTION ON THE SURFACE LAYER OF BUSHING ALLOY BY COUPLING BEM WITH ELASTICITY METHOD

In the design of the fatigue strength of dynamically loaded bearing in the equipmentssuch as internal combustion engines and roimg mun, the solution to the stress distribution on thebushing alloy layer is an important and difficult problem. In this paper, a new method has beenproposed by coupling BEM with etheticity method, The algorithm and its implementation were deseribed in details The calculation results verify that this up-dated method can provide us a moresimple and effective tool for solvingthe fatigue stress of the bushing alloy with tangible benefit oftime-saving and high computation accuraey. It may open a new vista in bearing fatigue strength design.

Investigation on Cracking in the Surfacing Welding Layer of Ni_3Al Based Alloy

Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.

A corrosion-resistant zinc-chromium alloy layer for highly reversible aqueous zinc-ion batteries

Aqueous zinc-ion batteries(AZIBs)are promising energy storage systems because of their inherent safety and excellent sustainability.In this study,a zinc-chromium alloy layer is electrochemically deposited on the Zn anode(ZnCr@Zn)to enhance its performance in aqueous electrolytes.The ZnCr alloy layer can effectively modulate and homogenize Zn^(2+)flux,thus significantly promoting uniform Zn deposition.Meanwhile,the corrosion-resistant ZnCr alloy layer protects Zn from detrimental side reactions,improving Zn plating/stripping reversibility.Consequently,the ZnCr@Zn anode achieves a high average Coulombic efficiency of 99.9%at 2 mA/cm^(2)over 600 cycles.Furthermore,the ZnCr@Zn||NH_(4)V_(4)O_(10)coin cell reliably operates for over 2000 cycles at 2 A/g with a capacity retention rate of 88.7%.The ZnCr@Zn||NH_(4)V_(4)O_(10)pouch cell also demonstrates excellent stability over 160 cycles at a current density of 0.5 A/g.This work provides a facile approach to improve the Zn anode for high-performance AZIBs.

Corrosion Resistance of AZ91 Magnesium Alloy after Laser Remelting Treatment

The main objective of the study was the modification of the surface layer of magnesium alloy by the COlaser. The studied material was the commercial AZ91 magnesium alloy. The effectiveness of the alternations caused by the remelting process was verified on the basis of microscopic observation and corrosion investigations, i e, recording of potentiodynamic polarization curves, electrochemical noise measurements and hydrogen evolution rate measurements. For the adopted range of the treatment parameters, favourable changes were observed in the surface layer such as the refinement of structure and more uniform arrangement of individual phases. As a consequence of those favourable structural changes the improvement of the corrosion resistance of the alloy was achieved in comparison to its non-remelted equivalent. For the treated material corrosion rates expressed as corrosion current densities were at least three times lower than the appropriate values for the untreated alloy comparing them for the same period of samples immersion in the test solution. The obtained results have confirmed the effectiveness of the applied surface treatment resulting in favourable changes in the structure and corrosion properties of the AZ91 magnesium alloy.

Alloying cobalt with ruthenium in nitrogen doped graphene layers for developing highly active hydrogen evolution electrocatalysts in alkaline media

Subject Code:B01With the support by the National Natural Science Foundation of China,a creative study by the research group led by Prof.Chen Qianwang(陈乾旺)from the University of Science and Technology of China and High Magnetic Field Laboratory,Hefei Institutes of Physical Science,Chinese Academy of

Electrochemical Properties of Tungsten-Alloying-Modified AISI 430 Stainless Steel as Bipolar Plates for PEMFCs used in Marine Environment

To improve the corrosion resistance and surface electrical conductivity of AISI 430 stainless steel （430 SS） as bipolar plates for proton exchange membrane fuel cells （PEMFCs） used in marine environment, a tungsten alloying layer has been successfully prepared on 430 SS substrate via the plasma surface diffusion alloying technique. The tungsten- modified （W-modified） 430 SS displays a 7-8 Ixm tungsten alloying layer with a body-centered-cubic structure. The W-modified surface also shows a better hydrophobicity with contact angle of 93.5~ and a lower interfacial contact resistance compared with the untreated 430 SS. The potentiodynamic and potentiostatic polarization and electrochemical impedance spectroscopy measurements show that the corrosion resistance of 430 SS is obviously improved in simulated PEMFC environment （0.05 M H2SO4 ＋ 2 ppm HF ＋ 0.01 M NaC1 solution at 70℃）, after the plasma surface diffusion alloying process.

Preparation and wear properties of high-vanadium alloy composite layer

A high-vanadium alloy composite layer was prepared on the surface of a carbon steel using cast composite technology,and the wear properties of the composite layer were investigated.The results showed that the microstructure of the composite layer was composed of primary vanadium carbides(VC),flake martensite,residual austenite,and fine VC.The hardness of the cast alloy layer was 63 HRC.The abrasive wear resistance and impact wear resistance were increased by 60%and 26%,respectively,compared with those of high-chromium cast iron.The excellent wear resistance of the cast alloy layer is attributed to the high-hardness primary vanadium carbide and the large number of fine secondary vanadium carbides precipitated out of the cast alloy layer.

Surface alloying of Al films/Ti substrate based on high-current pulsed electron beams irradiation

Ti–Al surface alloy was fabricated using a cyclic pulsed liquid-phase mixing of predeposited 100 nm Al film with a-Ti substrate by low-energy high-current electron beam. Electron probe micro-analysis（EPMA）,grazing incidence X-ray diffraction analysis（GIXRD）,transmission electron microscopy（TEM）, and nanoindentation were used to investigate the characterization of Ti–Al surface alloy. The experimental results show that the thickness of alloy layer is ＊3 lm, and the content of Al in the ＊1 lm thickness surface layer is ＊60 at%. The tetragonal TiAl and TiAl2intermetallics were synthesized at the top surface, which have nanocrystalline structure.The main phase formed in the ＊2.5 lm thick surface is TiAl, and there are few TiAl2and Ti3Al phase for the alloy.Dislocation is enhanced in the alloyed layer. The nanohardness of Ti–Al surface alloy increased significantly compared with a-Ti substrate due to the nanostructure and enhanced dislocation. Since the e-beam remelted repeatedly, the Ti–Al surface alloy mixed sufficiently with Ti substrate. Moreover, there is no obvious boundary between the alloyed layer and substrate.

Stable sodium metal anode enabled by interfacial room-temperature liquid metal engineering for high-performance sodium–sulfur batteries with carbonate-based electrolyte

Sodium(Na)metal is a competitive anode for next-generation energy storage applications in view of its low cost and high-energy density.However,the uncontrolled side reactions,unstable solid electrolyte interphase(SEI)and dendrite growth at the electrode/electrolyte interfaces impede the practical application of Na metal as anode.Herein,a heterogeneous Na-based alloys interfacial protective layer is constructed in situ on the surface of Na foil by self-diffusion of liquid metal at room temperature,named“HAIP Na.”The interfacial Na-based alloys layer with good electrolyte wettability and strong sodiophilicity,and assisted in the construction of NaF-rich SEI.By means of direct visualization and theoretical simulation,we verify that the interfacial Na-based alloys layer enabling uniform Na^(+)flux deposition and suppressing the dendrite growth.As a result,in the carbonate-based electrolyte,the HAIP Na||HAIP Na symmetric cells exhibit a remarkably enhanced cycling life for more than 650 h with a capacity of 1mAh cm^(−2)at a current density of 1mAcm^(−2).When the HAIP Na anode is paired with sulfurized polyacrylonitrile(SPAN)cathode,the SPAN||HAIP Na full cells demonstrate excellent rate performance and cycling stability.

Optimizing electronic structure of NiFe LDH with Mn-doping and Fe_(0.64)Ni_(0.36)alloy for alkaline water oxidation under industrial current density

Alkaline electrolyzers for water splitting under the industrial current densities are always burdened with huge energy consumption due to the high overpotential and poor stability of the anode nanocatalysts for oxygen evolution reaction(OER).Inspired by the interfacial charge transfer for enhancing the performance,a series of in-situ grown interfacial Mn-NiFe lactate dehydrogenase(LDH)was designed on the Fe_(0.64)Ni_(0.36)/NM(nickel mesh)alloy layer.The optimized Mn_(0.15)-NiFe LDH/Fe_(0.64)Ni_(0.36)/NM exhibited an ultralow overpotential of 295 mV to drive 500 mA·cm^(-2)and an incredible stability under large current density.The interfacial space and heteroatom doping synergistically triggered the electronic structure optimization to promote electron transfer and ensure the durability of the high-current reaction.Notably,the designed Mn_(0.15)-NiFe LDH/Fe_(0.64)Ni_(0.36)/NM as an anode in an integral alkaline electrolyzer exhibited a cell voltage of 1.78 V at 500 mA·cm^(-2) with a stability of 366 h.Density functional theory(DFT)calculations further demonstrated the synergistic effect of alloy layer introduction and Mn doping could accelerate electron transfer and stabilize the charged active center to activate the NiFe LDH and reduce the OER energy barrier.Our work offers new insights into developing efficient self-supported catalysts for high-current alkaline water oxidation.

Corrosion Behavior of Rusted 550 MPa Grade Offshore Platform Steel

The corrosion behavior of a rusted 550 MPa grade offshore platform steel in Clcontaining environment was investigated.The results revealed that the corrosion process can be divided into initial stage in which corrosion rate increased with accumulation of corrosion products and later stage in which homogeneous and compact rust layer started to protect steel substrate out of corrosion mediums.On the contrary,structural analysis of rust layers by X-ray diffraction showed that α-FeOOH increased from 1.3% to 3.6% and the Fe3O4 increased from 1.0% to 1.5% while γ-FeOOH reduced slightly according to corrosion time increased from 30 cycles to 73 cycles.The results of electron probe microanalysis indicated that Cr concentrated mainly in the inner region of the rust,inner/outer interface especially,whereas Ni and Cu were uniformly distributed all over the rust after 73 corrosion cycles.According to electrochemical measurements,it was found that the corrosion rate of rusted steel reduced from 0.61 mm/a after 45 cycles to 0.34 mm/a after 85 cycles,44.3% reduction approximately,and Rrust values increased with increment of corrosion time.Therefore,formation of compact inner rust layer and enrichment of Cr are important to improve corrosion resistance of offshore platform steel.

Electropolishing of titanium alloy under hydrodynamic mode

Titanium(Ti) alloys are widely used in aerospace industry due to the low density and high corrosion resistance. However, machining and polishing remain great challenges because of the hardness and chemical stability. With a home-made electrochemical machining workstation, cyclic voltammetry is performed at a wide potential range of [0 V, 20 V] to record the details of passivation and depassivation processes under a hydrodynamic mode. The results show that the thickness of viscous layer formed on the alloy surface plays a crucial effect on the electropolishing quality. The technical parameters, including the mechanical motion rate, polishing time and electrode gap, are optimized to achieve a surface roughness less than 1.9 nm, which shows a prospective application in the electrochemical machining of Ti and it alloys.

Effect of Surface Mechanical Attrition Treatment on Tribological Behavior of the AZ31 Alloy

By surface mechanical attrition treatment（SMAT）,a gradient nano structure（GNS） from the surface to center was generated in the AZ31 alloy sheet.The tribological behavior of AZ31 alloy with GNS was systematically investigated by using dry sliding tests,a 3D surface profile-meter and a scanning electron microscope equipped with an energy-dispersive spectrometer.The experimental results indicate that the Mg alloy with GNS exhibits better wear resistance comparing to the as-received sample,which is associated to the alteration of wear mechanism at different sliding speeds.The Mg alloy with GNS presents the wear mechanism of the abrasive wear at 0.05 m/s and the oxidative wear at 0.5 m/s,respectively.Moreover,the GNS can effectively promote the reaction between the oxygen and worn surface,which leads to a compact oxidation layer at 0.5 m/s.The effect of oxidation layer on the wear resistance of the Mg alloy was also discussed.