Li Wen Tang

Characterization and Modification of Nitrile Rubber in the Transformer Oil

The thermal aging experiments on nitrile rubber (NBR) and modified NBR were carried out in 25# transformer oil. Both of the content of CH4, microstructure, morphology and mechanics characterization was analyzed by Gas Chromatography (GC), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Servo Control material testing machine, respectively. The results shows that the amount of CH4 released from the modified NBR is less than original NBR, and the mechanics characterization of the modified NBR is also satisfied with the application requirements.

Phase Selection in Undercooled Cu85Cr15 Composites

Phase selection of undercooled Cu85Cr15 composites was analyzed by using different solidification conditions. The results revealed that the arc melted composites generally have non-uniform Cr-rich dendrites distributes on Cu-rich matrix. Due to strong electromagnetic stirring, uniform Cr-rich dendrites distributes on Cu-rich matrix for electromagnetic levitation melted composites. Both fine Cr-rich dendrites and Cr-rich particles coexisted in Cu-rich matrix for splat quenched composites, which means liquid phase separation occurred for the high cooling rate.

Microstructure Evolution of Hypereutectic Cu98Cr2 Alloys

Hypereutectic Cu98Cr2 alloys were prepared by vacuum arc melting and electromagnetic levitationing method. The microstructure evolution was investigated during the solidification process. It is shown that for the arc melted hypereutectic Cu98Cr2 alloy, the general microstructures consist of primary β(Cr) grains distributes on α(Cu) matrix and (α+β) eutectics set in cellular α (Cu) phase. However, due to the different solidification rate, the primary β(Cr) phase, (α+β) eutectics and α(Cu) phase coexist for the electromagnetic levitated hypereutectic Cu98Cr2 alloy. The reason for the different microstructure and evolution for the hypereutectic Cu98Cr2 alloy is studied in this paper.

The Numerical Simulation of Multi-Directional Forging EQ153 Steering Knuckle

This paper centers on EQ153 steering knuckle multi-directional forging forming, and applying Deform-3D to simulation the deformation process. According to temperature, effective strain, load prediction and final forging shape to illustrate in such a process a near-net-shape forming with no flash and little draft angle and lower pressure is been formed.

Influences of Surface Nanocrystallization Induced by High-Energy Spot Peening on Microstructure and Properties of Magnesium Alloy

As relatively new structure materials, magnesium and its alloys demonstrated significant potential for applications in many industries. However, magnesium alloys were easy to be corroded which greatly limited their development. AZ31B and AZ91D, two widely used commercial magnesium alloys in various industries, were chosen to be produced nanostructure on the surface layer, called Surface Nanocrystallization (SNC) by High Energy Spot Peening (HESP). The microstructure was characterized by Scan Electronic Microscopy (SEM) and X-ray diffraction (XRD) in this paper. Microhardness and corrosion resistance were measured by microhardness tester and electrochemical measurement system respectively. Experimental results showed that after HESP the grain sizes in the surface layer were obviously reduced into nanoscale; microhardness was greatly increased in the treated surface, about two times as much as that of original and corrosion current density in polarization curve was evidently raised while corrosion potential changed little.

Solidification Behavior of Undercooled Cu98Cr2 Alloys

The solidification behavior of undercooled Cu98Cr2 alloys was investigated under different rapid solidification methods. The results shown that whole lamellar (α+β) eutectics appeared in melt spun alloys for the sample undercooled into the coupled zone. The microstructure of arc melted Cu98Cr2 alloys consisted of primary β(Cr) particles distributes on α(Cu) matrix and (α+β) eutectics set in cellular α (Cu) phase. However, due to the different thickness and different solidification rate, the microstructure of splat quenched Cu98Cr2 alloys shown that only cellular supersaturated α solid solution occurred for thin flake and primary β(Cr) particles and (α+β) eutectics occurred for thicker flakes.

Numerical Simulation on Rapidly Solidified Melt Spinning CuFe10 Alloys

The numerical simulation model of single roller rapid solidification melt-spinning CuFe10 alloys was built in this paper. The vacuum chamber, cooling roller and sample were taken into account as a holistic heat system. Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapids solidification process of CuFe10 ribbons prepared by melt spinning can be approximately modeled by one-dimensional heat conduction equation, so that the temperature distribution and the cooling rate of the ribbon can be determined by the integration of this equation. The simulative results are coincident very well with the microstructure of rapid solidification melt spinnng CuFe10 alloys at three different wheel speeds 4, 12 and 36 m/s.

Numerical Simulation on Splat-Quenched CuCr25 Alloys

The numerical simulation model of rapid solidification splat-quenching CuCr25 alloys was built in this paper. The vacuum chamber, cooling cooper plate and sample were taken into account as a holistic heat system. Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapids solidification process of CuCr25 flakes prepared by splat-quenching can be approximately modeled by one-dimensional heat conduction equation, so that the temperature distribution and the cooling rate of the flake can be determined by the integration of this equation. The simulative results are coincident very well with the experimental results for the microstructure of rapid solidification splat-quenched CuCr25 alloys.

Microstructure of Cu75Cr25 Alloys under Different Conditions

The microstructure of Cu75Cr25 alloys was investigated by using vacuum non-consumable arc melting, electromagnetic levitation and splat quenching. The microstructure and solidification behavior of the Cr-rich were investigated by scanning electron microscopy (SEM). The results showed that inhomogeneous Cr-rich dendrite distributes on Cu-rich matrix for arc melted alloys. The microstructure consisting of a fine dispersion of Cr-rich dendrite in a Cu-rich matrix for electromagnetic levitated alloys. However, the morphology and size of the Cr-rich phase vary greatly with the cooling rate for splat quenched alloys. The Cr-rich phase show both dendrites and spheroids, this means liquid phase separation occurred during rapid solidification.

Microstructure Study of Undercooled Hypereutectic Cu95Cr5 Alloys

Microstructure of Cr-rich phase in undercooled hypereutectic Cu95Cr5 alloys was studied by using arc melting, electromagntic levitation melting and splat quenching. The results showed that the alloys generally have a microstructure consisting of a fine Cr-rich dendrites in a Cu-rich matrix. Even there existed strong electromagnetic stirring during solidification process, the nonhomogeneous Cr-rich dendrites were observed in electromagnetic levitation melted alloys. However, fine homogenous primary Cr-rich particles or equiaxed Cr-rich grains distributed in the Cu-rich matrix in splat quenched alloys.