G.S. Zhou

Electrotribological behavior of Cu−Ag−Zr contact wire against copper-base strip

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.

Effect of Cerium on Gas Evolution Behavior of Pb-Ca-Sn Alloy

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.

Evaluation of Ni Film Interfacial Energy Release Rate on Titanium and Stainless Steel Substrates

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.

Electrotribological property of the Cu−Ag−Cr alloy with high-strength and high-conductivity

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.

Electron theory based explanation and experimental study on deformation behavior of Cu/Ni multilayers

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.