M. Zheng
Xi'an Jiaotong University
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Featured researches published by M. Zheng.
Corrosion | 2006
Guanfa Lin; M. Zheng; Z.Q. Bai; Xinwei Zhao
Abstract Carbon dioxide (CO2) corrosion product scales of three kinds of oil well steel were obtained from simulated tests in autoclaves at varying temperatures and pressures. The effect of tempera...
Journal of Iron and Steel Research International | 2006
Guanfa Lin; M. Zheng; Z.Q. Bai; Yao-rong Feng
To investigate the correlation between structure characteristics and wear resistance of CO2 corrosion product scales at high temperature and high pressure, an autoclave was used to prepare CO2 corrosion product scales on N80 steel in carbon dioxide corrosion environment. The correlation between wear resistance of the scales and many other factors, such as temperature, pressure, morphology, structure, velocity of fluid medium, sand grain size, and so on, was comparatively analyzed by a self-assembled wear device, and the scale morphologies before or after being worn were observed by scanning electron microscope (SEM). And then the surface grain size and thickness of scale were measured. The results showed that the cross-section of the corrosion scale was of a double-layer structure, the outer layer of which was composed of regular crystals, whereas the inner layer was a thin scale of fine grains. The outer grain size and thickness of scale varied with temperature, and the initial wear loss was consistent with the surface grain size; at the same time, the total wear loss corresponded to the thickness of scale. Compared to wear resistance in different depths of the scale, it was found that the structure of scale was a doublelayer structure in cross-section, and the wear resistance of inner layer was better than that of the outer layer; the closer the scale to the matrix, the greater was the wear resistance of scale; and the larger the size or the higher the rotary speed of solid grain in multiphase flowing medium, the more was the wear loss of scale.
Metals and Materials International | 2005
G. X. Zhao; M. Zheng; X. H. Lv; X. H. Dong; H. L. Li
The corrosion behavior of 13Cr martensitic stainless steel in a CO2 environment in a stimulated oilfield was studied with potentiodynamic polarization and the impedance spectra technique. The results showed that the microstructure of the surface scale clearly changed with temperature. This decreased the sensitivity of pitting corrosion and increased the tendency toward general (or uniform) corrosion. The capacitance, the charge transfer resistance, and the polarization resistance of the corrosion product scale decrease with increasing temperature from 90 to 120 °C, and thus the corrosion is a thermal activation controlled process. Charge transfer through the scale is difficult and the corrosion is controlled by a diffusion process at a temperature of 150 °C. Resistance charge transfer through the corrosion product layer is higher than that in the passive film.
Metals and Materials International | 2005
Shuguo Jia; Ping Liu; Fengzhang Ren; Baohong Tian; M. Zheng; G.S. Zhou
Cu−Ag−Zr alloy has an excellent combination of mechanical strength and electrical conductivity, and is a promising contact wire material for high-speed electrified railways. An investigation of the electritrobological behavior of Cu−Ag−Zr wire is presented here. Wear tests are conducted under laboratory conditions with a specified sliding wear tester that simulated train motion under an electrical current applied across the sliding interface. The Cu−Ag−Zr alloy wire is slid against a copper-based powder metallurgy strip used in railway systems under unlubricated conditions. Worn surfaces of the Cu−Ag−Zr alloy wire are analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS). Within the studied range of electrical current, normal pressure, and sliding speed, the wear rate increases with increasing electrical current and sliding distance. Adhesive wear, abrasive wear, and electrical erosion are the dominant mechanisms during the electrical sliding processes. Compared with a Cu−Ag contact wire under the same test conditions, the Cu−Ag−Zr alloy wire has much better wear resistance.
Journal of Rare Earths | 2006
Guanfa Lin; G.S. Zhou; Dangguo Li; M. Zheng
Abstract The effect of Ce on the behavior of gas evolution on Pb-Ca-Sn alloy in 4.5 mol * L −1 H 2 SO 4 was investigated using cyclic voltammetry (CV), cathodic polarization curves and AC impedance (EIS). Cyclic voltammetry experiments show that the current of oxygen evolution on Pb-Ca-Sn-Ce electrode is lower than that of Pb-Ca-Sn electrode in the same anodic voltage. Moreover, the oxygen evolution potential on the former electrode is greater than that on the latter, and this means that Ce can increase the potential of oxygen evolution on Pb-Ca-Sn alloy. The AC impedance experiments show that Ce can also enhance the resistance of hydrogen evolution on Pb-Ca-Sn electrode, i.e., Ce can inhibit the hydrogen evolution on Pb-Ca-Sn electrode. The reason why Ce decreases the volume of hydrogen evolution on Pb-Ca-Sn alloy is that Ce increases the resistance of absorbing step of hydrogen evolution reaction. All the experimental results indicate that Pb-Ca-Sn-Ce alloy can rapidly decrease the oxygen and hydrogen evolution on Pb-Ca-Sn-Ce alloy. It is concluded that Pb-Ca-Sn-Ce alloy can promote the maintenance-free property of lead acid battery, and can serve as the candidate of the grid material for maintenance-free lead acid battery.
Metals and Materials International | 2002
Fengzhang Ren; W. Z. Zhao; G.S. Zhou; X. H. Ju; M. Zheng
An expression including the effect of residual stress on the interfacial energy release rate is proposed for peeling experiments according to the energy-balance argument. The influence of residual stress on the external work is also contained in the expression. Two numerical methods are employed to evaluate the values of the work expenditureGdb, which is the actual energy dissipated during bending of the peel arm near the peel front. The peeling method is employed to test the interfacial energy release rates,G, for Ni films on Titanium and stainless steel substrates. The results indicate that the value ofG for Ni films on stainless steel substrate is about 5.47–6.03 N/m, while 5.23–6.71 N/m for Ni films on titanium substrate; the interfacial energy release rates,G, do not depend on the residual stress in film, film thickness nor peel angle. The effect of residual stress in film on peel strengthP/h is also discussed.
Metals and Materials International | 2007
Shuguo Jia; Ping Liu; Fengzhang Ren; Baohong Tian; M. Zheng; G.S. Zhou
By means of a vacuum induction furnace, a Cu−Ag−Cr alloy was produced. The electrotribological property and mechanism of the Cu−Ag−Cr alloy wear studied via wear property tests, scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDS) and transmission electron microscopy (TEM). Wear tests were conducted with a specially designed sliding wear tester, which simulated the tribological conditions of sliding current collectors on contact wires in a railway system. The alloy wire was slid against a copperbased powder metallurgy strip under non-lubricated conditions. The results showed that the wear rate of Cu−Ag−Cr alloy increases as the sliding speed increases under a normal load. Adhesive wear, abrasive wear, and electrical erosion wear are the governing wear mechanisms under the electrical current sliding processes. Under the same conditions, the wear resistance of the Cu−Ag−Cr alloy is 2–3 times that of the Cu−Ag alloy.
Metals and Materials International | 2004
Fengzhang Ren; Ping Liu; M. Zheng; Q. M. Dong; G.S. Zhou; Q. Yuan
Cu/Ni multilayers with various defined thickness of Cu and Ni layers were electrodeposited on low carbon steel substrates. Hardness measurements indicated that the increase in yield strength (one-third of hardness) with a decrease of layer thickness for Cu/Ni multilayers with single layer thickness at sub-micron length scale could be described by the Hall-Petch formula of the dislocation pile-up model. In the regime of few tens to a hundred nanometers of single layer thickness, the dislocation pileup-based Hall-Petch model broke down. This could be explained quantitatively according to the criterion condition on the limit size of dislocation derived from a modified Thomas-Fermi-Dirac electron theory.
Metals and Materials International | 2002
Xinwei Zhao; Jinheng Luo; M. Zheng; M. X. Lu; He Li
Considering such practical pipeline service conditions in the petroleum transportation field as corrosion from harmful media (H2S, CO2 etc.) and load from the pressure of flowing petroleum as key factors, the degradation of the mechanical properties of pipeline steels and the corresponding variations in stress states are studied. A damage variable is introduced to reflect the degradation in the mechanical properties of the pipeline due to corrosion. A diluted solution approach is proposed to model the corrosion process of harmful media within the pipeline and the distribution of the damage variable along the radial direction of the pipeline is derived. An approach to the safety evaluation of damaged pipeline is proposed by comparing the instant properties of pipeline steels with servicing conditions.
Metals and Materials International | 2005
M. Zheng; J. B. Li; X. X. Shu
AbstractIn practical service, transmitted pipelines may suffer from corrosion, which affects the safety of the component. For an engineering pipeline subjected to local corrosion, the pipe wall becomes thinner locally, and the bending load bearing capacity is inevitably reduced. Therefore, proper prediction of the bending resistance of a pipeline with locally corroded defects is very significant with respect to the safety assessement of a servicing pipeline. In the present paper, the effect of the length of local thinning in a pipe in the longitudinal direction is considered. A modification to the net-section collapse failure (NSC) criterion is then proposed. 3-point bending experiments for J55 pipe with artificially machined local thinning on the outer-surface of the pipe are conducted to verify the modified expression. Comparison of the predictions of the modified NSC with the experimental data indicates that the modified expression can predict the general variation tendency of the normalized bending resistance (M/M0) with the relative longitudinal defect lenght (n