Xian Liang Zhou

Effect of Corrosive Medium on the Corrosion Resistance of FeCrMoCB Amorphous Alloy Coating

The purpose of this study is to investigate the electrochemical properties of Fe44Cr16Mo16C18B6 amorphous alloy coating fabricated using high velocity oxygen fuel (HVOF) technology in 2.0M HCl and NaOH solution at room temperature(25°C). Based on the potentiodynamic polarization curves and Electrochemical Impedance Spectroscopy(EIS) testing results of coating in aqueous solutions of HCl and NaOH, the corrosion resistance of Fe44Cr16Mo16C18B6 amorphous alloy coating in HCl solution was superior to that in NaOH solution. The icorr was 1.487×10-5A·cm-2 in HClsolution and 1.107×10-4A·cm-2 in NaOH solution, while the Rt reach to 5.789×104Ω·cm2 and 9780Ω·cm2, respectively. On the other hand, these corrosion phenomenon could be better interpreted by R(Q(R(RQW)))(RL) and R(RL)(Q(R(CW))) equivalent circuit model, which were different from that of other Fe-based amorphous alloys in HCl and NaOH solution, respectively.

Study on Salt Fog Corrosion of FeCoCrMoCBY Amorphous/Nanocrystalline Alloy Coating

Fe-based amorphous alloy coating with a composition of Fe41Co7Cr15Mo14C15B6Y2 was prepared by high velocity fuel(HVOF) technique. The influence of heat treatment on crystalline behavior, the phase structure and corroded morphology of the coating was investigated by Differential Thermal Analysis(DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy(SEM), respectively. The experimental results indicate that the amorphous alloy coating exhibited a two-step crystallization process with crystallization peak temperature at 698°C and 822°C, respectively. Amorphous coating exhibits excellent corrosion resistance than that of the corresponding nano-crystalline coating with heat treatment at 700°C for 2h, 8h and 12h. Furthermore, the nano-crystalline coating annealed 700°C for 12h suffers slight homogeneity corrosion, which did not exhibit obvious pitting on comparison with coating holding 2h and 8h.

Thermal Expansion Behavior and Characteristic of SiCp/Al Composites

SiCp/Al composites were fabricated by ceramic mold freedom infiltration and pressureless infiltration, respectively. The microstructure and phases are analyzed by metallurgical microscope and coefficient of thermal expansion of SiCp/Al composites were tested by thermal dilatometer. The results show that SiCp/Al composites are compact and uniform. SiC particles were dispersed uniformly in Al matrix, and SiCp segregation was not found in composites. Under a certain SiCp size range, space between SiCp decreases with decreasing of SiCp size, and CTE of SiCp/Al composites also decreases with decreasing of particles size. Compared with CTE of composite with pure aluminum as matrix, CTE of composite with ZL101 as matrix is less. Under the annealing process, CTE of SiCp/Al composites with ZL101 as matrix is less than that with the solution and aging, which indicated that its dimensional stability of resisting to temperature fluctuation is better, and thermal expansion behavior and characteristic of SiCp/Al composites are also better.

The Electrochemical Characterization of Electrochemically Synthesized MnO2-Based Mixed Oxides for Supercapacitor Applications

Nanostructured elements, including: manganese-molybdenum (Mn-Mo) oxide, manganese-molybdenum-tungsten (Mn-Mo-W) oxide, manganese-molybdenum-iron (Mn-Mo-Fe) oxide, manganese-molybdenum-cobalt (Mn-Mo-Co) oxide, manganese-vanadium-tungsten (Mn-V-W) oxide, manganese-vanadium-iron (Mn-V-Fe) oxide and manganese-iron (Mn-Fe) oxide, have been anodically deposited onto titanium substrates by employing an iridium dioxide interlayer (Ti/IrO2 anode). The electrochemical characteristics of the resultant oxide deposits have been investigated by cyclic voltammetry (CV) in an aqueous 0.1 M Na2SO4 solution. The voltammetric behaviors of the oxide deposits observed are significantly influenced by the doped elements. Molybdenum doping is found to be advantageous at improving the capacitance characteristics of anodically deposited manganese oxide. Comparatively, iron and vanadium doping are found to be unfavorable. The structure and crystallinity of these deposits have been identified by X-ray diffraction (XRD). The surface morphologies of these oxides were acquired from field emission scanning electron microscopes (FESEM). The high values of electrical parameters for the doped deposits are attributed to the net-like and sponge-like nanostructure, and low crystallinity of the doped manganese oxides. The deposit of Mn-Mo oxides exhibits an excellent capacitive-like behavior, possessing the maximum specific capacitance of 810 F g-1 at a CV scan rate of 5 mV s-1 in aqueous 0.1 M Na2SO4 solution.

Influence of Mg and Si in the Aluminum on the Thermo-Physical Properties of Pressureless Infiltrated SiCp/Al Composites

SiCp/Al composites based on different matrix elements Mg and Si content were fabricated by pressureless infiltration. Through microscope investigation by SEM and TEM, density examination, coefficient of thermal expansion (CTE) and thermal conductivity measuring by Netzsch DIL 402EP and Netzsch LFA 447 Nanoflash, the effects of Mg and Si in the aluminum on the thermo-physical properties of SiCp/Al composites was studied and analysed. The results showed that , adding Mg element in matrix enhaced the densification and thermal conductivity of composites, but meanwhile increased the CTE of SiCp/Al composites. When Mg element content was in higher than 6.3wt%, CTE of SiCp/Al composites increased obviously. Adding Si element in matrix markedly reduced the CTE of composites , but meanwhile decreased thermal conductivity of composites. When Si element content was higher than 5-9wt%,thermal conductivity of composites declined obviously. Adding Mg element in matrix improved the interface wet ability between molten aluminum and SiC particles, and adding Si element in matrix could control the formation of A14C3 which is a detrimental interface reaction product during the pressureless infiltration processing. Therefore, adding appropriate Mg in company with Si in matrix will be more benefit to enhance the integer properties of SiCp/Al composites.

Microstructure and Property of the New Type White Cast Iron

The influences of the different Si (0.723%~4.5%) and Cr (2.0%~8.0%) contents on the microstructures and properties of Cr-Si-Mn white cast iron were investigated. It is shown that with increasing of amounts of Si and Cr elements, carbide undergoes an evident change in the morphology from the continuous net to isolated stripe and becomes clearly finer, even forms chrysanthemum-like microstructure which is usually found in high Cr white cast iron. Additionally, the amounts of the carbides increase too. The XRD analysis shows that the carbides are a mixture of Fe3C and Fe7C3 phases. Furthermore, the hardness of carbide and matrix is also found to progressively increase with increasing of amounts of Si and Cr elements. The hardness of the matrix in as-cast white cast iron is over HV400, suggesting that the matrix consists of martensite and bainite phases. The impact toughness of the samples declines evidently when Si content excesses 3.0wt%. It is also revealed that the bainite matrix in the Si-Cr white cast iron has a higher impact abrasive wear resistance than others, which is almost not dependent upon heating temperature and cooling rate. When Cr content approaches 5wt%, the impact wear resistance of the new cast iron is comparable to that of the traditional high Cr cast iron.

Salt Spray Corrosion Performance Associated with the Glass Forming Ability of the FeCo-Based Bulk Metallic Glasses

For the bulk amorphous Fe24+xCo24-xCr15Mo14C15B6Y2(X=0, 2, 4, 6 and 17) alloy, the corresponding corrosion properties associated with glass forming ability (GFA) have been carried out. Neutral salt spray corrosion test results show that the Fe28Co20Cr15Mo14C15B6Y2 alloy has the minimum corrosion rate, followed by Fe26Co22Cr15Mo14C15B6Y2, Fe24Co24Cr15Mo14C15B6Y2, Fe30Co18Cr15Mo14C15B6Y2, Fe41Co7Cr15Mo14C15B6Y2 and Ti6Al4V alloys. Specifically, the Fe28Co20Cr15Mo14C15B6Y2 alloy with the highest GFA also has the best corrosion resistance. With the increasing of Co addition, the corrosion resistance of the FeCo-based bulk metallic glasses is first increases and then decreases, which has the same trend of GFA with the change of Co elements. Furthermore, corrosion morphology are different for FeCo-based BMGs with different Co content.

Fabrication and Fracture Analyses of SiC Particulate-Reinforced Al Matrix Composites

The fabrication process and fracture characterization of 35 and 65 vol% SiCp particulate-reinforced Al matrix (SiCp/Al) composites have been investigated. SiCp composites having different volume fractions of the n-SiCp were synthesized via by pressureless-infiltration at near-net-shape route and were uniaxially tested at room temperature. The SiC particles were mixed with silicasol as an inorganic binder in distilled water. The mixtures were consolidated in a mold by pressing and dried in two step process, followed by calcination at 1000 °C. The SiCp/Al composites were fabricated by the infiltration of Al melt into SiC performs. The experimental results show that volume fraction of reinforced particles in SiCp/Al composites had a significant influenec on fracture section surface characterization in tensile tests. Composite with 45 vol% SiCp, fracture was firstly happen in Al matrix, shallow dimples and intergranular fractures were seen in all the fractographs. With increasing of vol% SiCp, fracture was more brittle in appearance in the composites and the fracture surfaces were flat and less plastic deformations.

Effects of Mg and Si in Al Matrix on Dimensional Stability of SiCp/Al Composites during Temperature Change

In this paper, based on the parameters of cumulative residual strain(CRS), the effects of different contents of Mg and Si elements in Al matrix on the dimensional stability of SiCp/Al composites was investigated and analyzed in the temperature interval of 25～400°C. Results show that，with the increasing of Si content in Al matrix, the CRS fluctuates only in a small range of strain, adding Si in Al matrix is beneficial to the dimensional stability of the composites, which can be improved through pre-thermal cycling; with the increasing of Mg content in Al matrix, the absolute value of negative CRS of the composites becomes smaller at the beginning and then turns positive, adding Mg in Al matrix causes the composites expand after several thermal cycling, it is not good to the dimensional stability of the composites and is quite impossible to be improved by pre-thermal cycling. Besides, the CRS in thermal cycling is mainly caused by the plastic relaxation, which results in the irreversible dimensional variation of about 10-5~10-4.

Effects of High Co Contents in Fe-Cr-Mo-C-B-Y Alloy on the Glass Forming and the Mechanical Properties

A series of wedge shape Fe24+XCo24-XCr15Mo14C15B6Y2 (x=0,2,4,6,8) samples were prepared by copper mold suction casting method. The effects of high Co contents on glass forming ability (GFA) and mechanical properties of Fe24+XCo24-X Cr15Mo14C15B6Y2 bulk metallic glasses (BMG) were investigated, respectively. The glass forming ability of bulk amorphous Fe24+XCo24-XCr15Mo14C15B6Y2 (x=0,2,4,6,8) and Fe41Co7Cr15Mo14C15B6Y2 alloys have been researched. Simultaneously, the thermal conductivity parameters of those alloys were tested. The maximum thickness of amorphous region of wedge-shaped samples are dm =7.80 mm for Fe28Co20Cr15Mo14C15B6Y2, dm =7.10 mm for Fe41Co7Cr15Mo14C15B6Y2 and the thermal conductivity are λ=7.11 w.m-1.k-1 and 7.19 w.m-1.k-1, the thermal diffusivity are α=1.875 mm2/s and 1.905 mm2/s for Fe28Co20Cr15Mo14C15B6Y2 and Fe41Co7Cr15Mo14C15B6Y2 BMGs, respectively. The glass forming ability of Fe28Co20Cr15Mo14C15B6Y2 alloy is bigger than that of well known Fe41Co7Cr15Mo14C15B6Y2 alloy. With the change of Co content, the Vickers hardness of Fe24+XCo24-XCr15Mo14C15B6Y2 (x=0,2,4,6,8) change from 1292 to 1322Hv.