Wen Yan Wang

Microstructure and Tensile Property of Zn-Al Alloy Reinforced with Titanium Produced by Electrolysis

In this study, some low-titanium aluminum alloys produced by electrolysis were prepared and the effect of various titanium contents on microstructure and tensile property of Zn-Al alloy was investigated. The test results showed that addition of titanium by electrolysis is an effective way to refine the grain size of Zn-Al alloy. As the titanium content is 0.04 wt%, the grain size becomes to be a minimum value and the tensile property of the alloy reaches to the maximum. Electrolysis showed that titanium atoms are to be some inherent particles in low-titanium aluminum alloy. These titanium atoms enter into the aluminum melt liquid and spread to the whole melt rapidly under stirring action of electromagnetic field of the electric current. The heterogeneous phase nuclei are high melting TiC and TiAl3 particles formed from in-situ precipitating trace C and Ti during cooling process. These in-situ precipitating heterogeneous nucleation sites with small dimension, high dispersity, cleaning interface and fine soakage with melt, have better capacity of heterogeneous nucleation than of exotic particles. It may inhibit grain growth faster and more effective in pinning dislocations, grain boundaries or sub-boundaries.

Study on the In Situ SEM Tension Observation of E-A356 Alloys

The fracture mechanisms of E-A356 alloys (T5 treatment) have been investigated by means of in situ SEM under nonaxial tension loading. It is found that the crack initiated at the casting defects, such as at the gas or the shrinkage pores, because of the debonding of the silicon particles from the Al matrix. The crack propagation was mainly in the Al matrix and along the matrix/particle interface secondarily. The crack growth could be influenced by the eutectic silicon particles, when it encountered the Si particles, the growth direction would be changed and turned toward the weaker areas. The fracture resistance or the mechanical properties of the E-A356 alloys will be improved by means of reducing, eliminating gas or shrinkage pores and increasing the interface bound strength of the eutectic silicon particles with the Al matrix.

Stress Field Numerical Simulation of the Inclusions in Large Rudder Arm Steel Casting

The influences of non-metallic inclusions on the quality and properties of the steel not only depended on the quantity of inclusions, but also on the type、shape、size、deformation behavior and distribution condition. By means of ANSYS finite element analysis software, the stress field distribution in the inclusions and the matrix around the inclusions are analyzed under the condition of different kinds of types、shapes、distributions with changeable load in heavy rudder arm steel castings, then micromechanics behavior of inclusions is investigated from angle of macro mechanics.

NiCr alloy Coating Deposited on the Surface of 35CrMo steel by the Electrospark Process

Strengthened coating on the surface of 35CrMo steel alloy was deposited by electrospark process using NiCr electrode. The bond strength and microhardness of the coating was checked and the microstructure of the strengthened coating was analyzed using the optical micro-scope, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrum (EDS). The results show that the bond strength between the coating and the base metal is 495.1MPa, and the hardness of the coating surface is about 2 times than that of the base metal, and the property of the workpieces surface has become better. The coating is a metallurgical reacting bonding layer between the base metal and the NiCr electrode, and its main ingredients are FeNi and NiCrFe.

Hot Deformation Behaviors and Microstructure Evolution of SiCp/Al Composites

In order to explore the compressive properties of aluminium matrix composite reinforced with middle content SiC particles, hot compression behavior of 30%SiCp/2024A1 composite was investigated using Gleeble-1500 system at a temperatures range from 350 to 500°C and strain rates from 0.01 to 10 s−1. The associated structural changes were studied by OM, SEM and TEM observations. The results show that the true stress–true strain curves exhibited a peak stress at a small strain (<0.1), after which the flow stresses decreased monotonically until high strains, showing a dynamic flow softening. The stress level decreased with increasing deformation temperature and decreasing strain rate, indicating that the composite is a positive strain rate sensitive material. And therefore there will be a enough time for dynamic recrystallization to complete nucleation and growth at low strain rate and high deformation temperatures.

Research of Friction and Wear Performance of Large Truck’s Brake Drum

In this research, different frictions were settled to study the wear resistance of HT250, RuT15, RuT75 and QT500 according to the wear failure situation in automobile brake drum. And the relationship between wear mechanism, microstructure and mechanical properties were discussed. It can be seen from the friction and wear experiment that, under different friction and wear conditions, both of RuT35 and QT500 have the best wear resistance property while HT250 has the worst wear resistance property. With the increase of lord, the brake torque and friction coefficient of RuT35 stays unchangeable, showing well brake ability. With the increase of lord, the brake ability of HT250 was getting better, while QT500 showing the opposite. SEM was used to analyze the wear morphology, the results show that: the abrasive wear and adhesion wear are presented mainly. HT250 has a bad surface quality while QT500 and RuT15 have a bad surface quality. Generally speaking, RuT15 is the best material to made brake drum, in the consideration of were resistance and braking stability.

Sol-Gel Derived Titania/Hydroxyapatite Layer on Titanium Substrate

In this study, calcium nitrate(Ca(NO3)2•4H2O) and phosphorus pentoxide(P2O5) were used as precursor to prepare hydroxyapatite(HA) layer by sol-gel method, followed by a dipping-coating method to coat HA layer onto Ti. Phase formation and microstructure were investigated by XRD and SEM to study the influence of atmosphere on the property of HA layer. The results revealed that there exists no large cracks in the layer which was heated in the nitrogen, leading to a good surface quality compared with the layer which was heated in the air. And there is no obvious difference in crystallinity and volume fraction of HA in the layer when adopting heat treatment in different atmospheres.

The Numerical Simulation of Microstress for Hypereutectic Al-Si Alloys

The elastic-plastic finite element mechanical model of hypereutectic Al-Si alloy was established based on ANSYS software. When the Si particles were circle, trapezium, rectangle or triangle, the microstress of Al-Si alloy under the external load were simulated. When the size of Si particles changed from 25μm to 45μm, the stress of Si particles and matrix interface was calculated. The effects of morphology and size of Si particles and loads on micro-mechanics characteristic of alloy were analyzed. The results showed that: under the same load, triangle or wedge angle Si particles make the biggest stress in the matrix, trapezoidal particles make the second and the spherical particles make the smallest. With the increase of the load, the stress and the stress concentration of Si particles in the matrix was increased, the stress of wedge angle particle increases remarkably, but the stress of spherical particles increases slowly. With the increase of the size of Si particles, the stress and the stress concentration of Si particles in matrix are increased.

Structure and Properties of Ductile Iron Strengthened by Laser Surface Alloying

The wear resistance, corrosion resistance, high temperature resistance layers were prepared on the surface of ductile iron via laser alloying process, using the mixed ponder of sub-micron carbides power as starting materials. The microstructures of the different laser alloying layers were characterized by XRD, SEM, EDS, TEM. The microhardness and wear resisitance of the laser alloying layers were examined. The results reveal that the flat alloyed coating combines metallurgically with the substrate. the laser area was composed by alloyed zone ,heat-affected zone and matrix zone. The alloyed zone was composed mainly by ledeburite and carbide, while martensite and retained austenite were contained in the heat affected zone, there is no significant change in the Matrix zone. Under conditions that the laser power, spot diameter remain unchanged, with in 400 ~ 1000 mm/min scanning speed, the hardness of alloyed coating increases with increasing scanning speed. The weightlessness of the alloyed samples under the dry sliding friction is one-sixteenth of ductile iron. The wear resisitance of the alloyed coating has improved significantly.

Friction and Wear Characteristics of Laser-Clad Nano-Lubricating Coating

Nickel-based nano self-lubricating coatings were deposited on medium carbon steel by laser. The microstructure and tribological properties of the typical coating containing 10wt % nano-hBN powders were investigated using SEM incorporating EDS, and high temperature tribo-tester, respectively. It was found that the cladding layer and substrate was good metallurgical bonding. Dry sliding frictional tests suggested that the composite coating containing about 10wt % hBN powders has lower friction coefficient than that of pure Ni60 cladding at room temperature with a load of 40N and a speed of 2m/s, as well as 400°C with a load of 20N and a speed of 2m/s. The wear resistance of Ni60-hBN coating is about 10 times than that of Ni60 coating. The SEM analysis of the abrasion morphology found that wear mechanism of self-solid lubrication coating was adhesive wear, and wear mechanism of the cladding layer of non-lubricant was adhesive wear with abrasive wear.