基于氯化胆碱的低共熔体系在Au上电沉积无枝晶Zn

以氯化胆碱和乙二醇混合液为低共熔溶剂,不使用其他添加剂,电化学沉积无枝晶Zn/Au合金。在不同的Zn(Ⅱ)浓度下,采用恒电位电沉积法在相对较低的Zn电沉积过电位下进行电沉积。通过循环伏安法(CV)和计时安培法(CA)揭示Zn电沉积的电化学机理。采用扫描电子显微镜和X射线衍射分析(XRD)对沉积层的形貌和结构进行表征,并用能谱仪对沉积层进行元素分析。CV结果表明,Zn的电沉积始于Zn欠电位沉积区,并一直持续到Zn过电位沉积(OPD)区。随着Zn(Ⅱ)浓度的增加,Zn/Zn(Ⅱ)电偶的沉积电位向更高的正值偏移。CA分析表明,在Zn的OPD区开始三维渐进形核,随后形成三维生长。形貌分析表明,电沉积始于致密Zn岛的形成,随后形成无枝晶Zn/Au合金。XRD分析表明,其物相为金属Zn、立方AuZn3和Au Zn金属间化合物。

INVESTIGATION ON MECHANICAL PROPERTIES OF ZN-AL/SIC PARTICULATE COMPOSITES

In order to improve the properties of ZA 27 and ZA4-3 zinc alloys and broaden their application ranges,SiC particlj1Ale composites, prepared by means of rheological casting technology, are investigated individually on their rT..t'llanical properties. The results of ne-cural strength, impact strensttl, compressive strength, hardness values and wear rate of the composites show that the addition of SiCp, leads to the increase of the compressive strength and hardness values at both room and higher temperature, and wear resistance of the materials, accompanying with the slight decrease of the fie-cural strength and sharp reduction of the impacttoughness. The factors affecting the mechanical properties of the composites are discussed in the paper.

HARDNESS PROPERTY AND WEAR RESISTANCE OF Al_2O_(3P)/ Zn-Al COMPOSITE

The hardness values and the wear resistance of Al2O3P/ Zn-Al composite, prepared by means of rheological casting technology,are investigated separately in this work. The results show that the addition of Al2O3P increases the hardness values of the matrix at both room and high temperature and improves the wear resistance of the material.The hardness values and the wear resistance of the composite rise with the increase of the particle volume fraction or the decrease of the particle size.The raising of test temperature results in a rapid descending of its hardness values.However, the addition of Al2O3P improves the property of high temperature resistance of Zn-Al alloys significantly.Moreover,the effect of quenching, tempering or cycling heat treatment on the hardness values of the composite is also studied.

Influence of alloying elements on microstructure and microhardness of Mg-Sn-Zn-based alloys

The phase evolution in （88%-91%）Mg-8%Sn-l%Zn-X （X=A1, Mn and/or Ce） system was analyzed via CALPHAD method and simulations were used in precise selection of the chemical composition. The influence of the addition of different alloying elements such as A1, Mn and Ce on the microstructure and microhardness of Mg-8%Sn-l%Zn-based alloys was investigated. Combined addition of A1 and Mn shows features distinct from separate addition of A1 or Mn. Additions of l%AI and l%Mn to base alloy result in the formation of massive A1-Mn phase in a-Mg matrix grains. Addition of Ce element can refme the second eutectic precipitates and form intermetallic compounds with Sn. Fine rod-like Sn-Ce phase presents mainly on the grain boundaries and plays a role in inhibiting grain growth. The effects of alloying elements on Vickers microhardness and indentation size effect of base alloy were examined.

Effect of Sb on microstructure and mechanical properties in Mg-10Zn-5Al high zinc magnesium alloys

In view of high strength and poor impact toughness of the high-zinc magnesium alloys,the method of micro-alloying was adopted to improve the impact-toughness of Mg-10Zn-5Al high zinc magnesium alloys by adjusting the addition of Sb.The results show that:the dystectic Mg3Sb2 particles formed by Sb and Mg are distributed in the front of dendrite,restrain the growth of the secondary phase and then change the morphology of the secondary phases,which refines the matrix in some extent and improves the impact-toughness of the alloy significantly.But with further increase of Sb addition,Mg3Sb2 particles congregate and form needle-like Mg3Sb2 phase,which dissevers the matrix and leads to the reduction of the strength and impact-toughness of the alloys.Hence,the mechanical prosperities of ZA105 high zinc magnesium alloy are significantly improved with appropriate Sb addition,which provides a new way to extend the application fields of high zinc magnesium alloy.

Fe-Zn supersaturated solid solution prepared by mechanical alloying and laser sintering to accelerate degradation

The slow degration of iron limits its bone implant application.The solid solution of Zn in Fe is expected to accelerate the degradation.In this work,mechanical alloying(MA)was used to prepare Fe-Zn powder with supersaturated solid solution.MA significantly decreased the lamellar spacing between particles,thus reducing the diffusion distance of solution atoms.Moreover,it caused a number of crystalline defects,which further promoted the solution diffusion.Subsequently,the MA-processed powder was consolidated into Fe-Zn part by laser sintering,which involved a partial melting/rapid solidification mechanism and retained the original supersaturated solid solution.Results proved that the Fe-Zn alloy became more susceptible with a lowered corrosion potential,and thereby an accelerated corrosion rate of(0.112±0.013)mm/year.Furthermore,it also exhibited favorable cell behavior.This work highlighted the advantage of MA combined with laser sintering for the preparation of Fe-Zn implant with improved degradation performance.

Microstructures and mechanical properties of Mg-2%Zn-0.4%RE alloys

The solidification microstructures and hardness of Mg-2%Zn (mass fraction) based alloys with addition of 0.4%Ce, 0.4%Gd, 0.4%Y or 0.4%Nd (mass fraction) were investigated, and the effects of the rare earth elements on the microstructures and mechanical properties of these alloys extruded at 310℃ were also compared. The results indicate that the trace rare earth Ce, Gd, Y or Nd in the Mg-2%Zn alloy has obviously different grain refinement effects on its solidification microstructures, and the as-cast and hot-extruded alloy with 0.4%Ce has the smallest average grain size and the highest strength. However, the extruded alloys containing 0.4%Nd or 0.4%Y with the elongation of 26.6% and 30%, respectively, show higher plasticity in spite of lower strength as compared with the alloy containing 0.4%Ce.

Effects of electromagnetic stirring on microstructure and mechanical properties of super light Mg-Li-Al-Zn alloy

Effects of electromagnetic stirring on the microstructure and mechanical properties of the magnesium-lithium-aluminum alloy were studied.The results reveal that,the morphology of theαphase changes from the long block to globular structure andβ phase distributes more widely in the periphery ofαphase when the electromagnetic stirring voltage is higher than 110 V.The mechanical properties are increased significantly with the increasing electromagnetic stirring.The tensile strength is improved from 172 to 195 MPa,and the elongation is increased from 10.65%to 25.75%.

Electrodeposition of Compositionally Modulated Zinc-cobalt Alloy Multilayer Coatings

The effects of pulse parameters on the cobalt content, surface morphologies and grain size of Zn-Co alloy deposits were studied using a pulse plating technique with a square-wave current containing reverse pulse. Average current density and reverse anodic current density amongst the variables investigated have very strong effects on the cobalt content in the Zn-Co alloy deposits. Grain size, surface appearance and internal stress in the deposit were improved significantly by introducing the reverse current. Varieties of Zn-Co alloy compositionally modulated multilayer (CMM) coatings with large differences in cobalt contents for different sublayers were electrodeposited by designing corresponding waveforms using a computer-aided pulse plater and characterized in terms of surface morphologies. Cross-sectional morphologies of the Zn-Co alloy CMM coatings, examined using field emission gun scanning electron microscopy (FEGSEM), confirmed the layered structure.

Effects of Y and Zn on mechanical properties and damping capacity of Mg-Cu-Mn alloy

Optical microscope,X-ray diffractometer,scanning electron microscope,tensile tester and dynamic mechanical analyzer(DMA) were applied to investigate the effects of Y and Zn additions on microstructure,mechanical properties and damping capacity of Mg-3Cu-1Mn(CM31) alloy.The results show that with the increase of Y and Zn contents,the secondary dendrite arm spacing of alloys is reduced;meanwhile,the yield strength is increased.In low strain amplitude,the damping capacity of alloys with Y and Zn addition is lower than that of CM31 alloy.However,in strain amplitude over 5×10-3,the damping capacity of alloy with a trace of Y and Zn addition(1%Y and 2%Zn,mass fraction) increases abnormally with the increase of strain amplitude and is near to that of pure Mg,probably due to the increase of dislocation density caused by the precipitation of secondary phase.The temperature dependence of damping capacity of above alloy was also tested and discussed.

Improvement in the liquid zinc corrosion resistance of high Nb-TiAl alloys by pre-oxidation in a SiO_2-powder pack

The influence of pre-oxidation on the liquid zinc corrosion resistance of high Nb-TiAl alloys was investigated. The pre-oxidation was performed by heating the specimens, buried in silica powder and encapsulated in a silica tube under a vacuum of 1.3x10-5 Pa at 950℃ for 12 h. Experimental results showed that the preoxidized sample exhibited much higher liquid zinc corrosion resistance than that for the comparative samples. This excellent liquid zinc corrosion resistance was attributed to the formation of high-quality oxide scale during peroxidation. The corrosion of all the samples in liquid zinc was caused by a localized breakdown in the oxide scales. The continuous and dense oxide scale formed during preoxidation substantially may prevent the liquid zinc from diffusing to the substrate, and its good continuity may also reduce the possibility of localized breakdown in the oxide scale.

A theoretical study of the influence of dopants on the dehydrogenation properties of VH_2

Using the plane wave ultrasoft pseudopotential method based on the first-principles density functional theory(DFT),the influence on the electronic structure and dehydrogenation properties of VH2 doped with Zr,Cu and Zn has been studied.The results show that the negative heat of formation increases and the valence electron number at the Fermi level EF,N(EF) decreases in the Zr-doped model,indicating the higher stability of VH2 after Zr alloying.On the other hand,the negative heat of formation of VH2 decreases and the N(EF) increases in Cu-or Zn-doped systems,suggesting the lower stability of VH2 after Cu or Zn alloying.The calculated overlap populations and electron densities of the V-H bond demonstrate that the bonding is strengthened by Zr doping and weakened by Cu or Zn doping.The results predict that the maximum capacity to absorb and desorb hydrogen can be raised by the introduction of Zr and reduced by the introduction of Cu or Zn,while the dehydrogenation properties will be poorer in Zr-doped systems and enhanced in Cu-or Zn-doped systems.These predictions are consistent with the experimental results.Mulliken populations were also calculated and it was found that the Mulliken population of the V 3d orbitals decreased as a result of Zr doping,and increased after Cu or Zn doping.