Jian Ming Wang

Effects of Particle Size and Volume Fraction on Extrusion Texture of SiCp/Al Metal Matrix Composites

The texture development was investigated in the extruded Al and Al metal matrix composites (MMCs) reinforced with SiC particles of different sizes and volume fractions. During extrusion, both the unreinforced Al and the MMCs develop a strong fiber texture with two components: <111> and <100>. When SiC is introduced into aluminum, the main component of texture is not modified, but the intensity of the component evolves with the volume fraction and average size of SiC particles. For the MMCs reinforced with 3.5μm SiC particles, the texture intensity of the Al matrix tends to decrease as the SiC volume fraction increases, and it is lower than that in the unreinforced Al. However, for the MMCs reinforced with 25 nm and 150 nm SiC particles, the texture intensity of the Al matrix is higher than that in the unreinforced matrix, and it increases with increasing the SiC volume fraction. It is found that superfine particles may introduce some new component into the deformation texture, and the texture intensity increases as the SiC particle size decreases.

Effects of Heat Treatment Process on Mechanical Properties of X70 Grade Pipeline Steel Bends

Effects of heat treatment process of quenching and tempering under different temperature conditions on mechanical properties of X70 grade pipeline steel bends were studied. Brinell hardness, yield strength, tensile strength, elongation and impact absorbing energy of the bends were tested by using hardness tester, cupping machine and impact testing machine, respectively. It shows that the best heat treatment process of the X70 grade pipeline steel bends is quenching at 890 °Cand thermal insulation for 26 min then water cooling followed by tempering at 590 °C and thermal insulation for 60 min then air cooling. Furthermore, the resulting hardness, yield strength, tensile strength, yield ratio, elongation and impact absorbing energy reach HB230, 595 MPa, 725 MPa, 0.82, 28% and 300 J respectively, which has excellent comprehensive mechanical properties.

Influence of bias voltage on structure, mechanical and corrosion properties of reactively sputtered nanocrystalline TiN films

Nanocrystalline TiN films were prepared by DC reactive magnetron sputtering. The influence of substrate biases on structure, mechanical and corrosion properties of the deposited films was studied using X-ray diffraction, field emission scanning electron microscopy, nanoindentation and electrochemical techniques. The deposited films have a columnar structure, and their preferential orientation strongly depends on bias voltage. The preferential orientations change from (200) plane at low bias to (111) plane at moderate bias and then to (220) plane at relatively high bias. Nanohardness H, elastic modulus E, H/E* and H3/E*2 ratios, and corrosion resistance of the deposited films increase first and then decrease with the increase in bias voltage. All the best values appear at bias of −120 V, attributing to the film with a fine, compact and less defective structure. This demonstrates that there is a close relation among microstructure, mechanical and corrosion properties of the TiN films, and the film with the best mechanical property can also provide the most effective corrosion protection.

High temperature oxidation resistance of CrN/(Ti, Al, Zr, Cr)N bilayer films deposited by multi-arc ion plating

CrN/(Ti, Al, Zr, Cr) N bilayer films were successfully deposited on cemented carbide (WC-8%Co) substrates by multi-arc ion plating process using two Ti-Al-Zr alloy targets and one pure Cr target. As a result of bilayered structure and addition of alloying elements (e. g. Al and Cr), the films exhibited excellent high temperature oxidation resistance under both short-term isothermal (up to 800 °C) and long-term cyclic (up to 600 °C) exposure conditions. Combined with pre-established outstanding tribological properties (e. g. maximum hardness of 4000 HV0.01 and maximum adhesion strength over 200 N), these observations make such films quite a promising candidate to extend the cutting tool life span and boost the performance in high-productivity, high-speed and high-feed cutting or in dry machining conditions.

Study on Improving the Performance of X80 Pipeline Steel

This paper analyzes the methods of improving the performance of X80 pipeline steel. In the process of manufacturing piping, the right temperature of coiling the steel can improve the comprehensive mechanical properties of X80 pipeline steel. The proper cooling rate can make heat affected zone get the good performance. Quenching can improve the performance of X80 pipeline steel, but the temperature can not be too high. At the same time, the appropriate tempering treatment can make X80 pipeline steel obtain good hardness, strength, plasticity and toughness.

Effect of Calcium and Magnesium Addition on the Inclusions Distribution in the Cast Microstructure of HSLA Steel

A new technology to obtain a fine-structured and high-toughness HAZ of HSLA steel for high heat input welding is developed using metallurgical thermodynamics, physical chemistry of metallurgy and material processing methods synthetically in this study. A kind of HSLA steel is designed in this experiment. The thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding calcium and magnesium into the steel in the form of Si-Ca alloy and Mg-Zr alloy, respectively. The effect of calcium and magnesium addition on the morphology and distribution of the inclusions in the cast microstructure of HSLA steel was analysed. The results show that the distribution of the inclusions is more dense and uniform with respect to the raw steel, and the size of the inclusions is smaller than the ones in the raw steel after adding Ca and Mg elements. Ca and Mg elements can accelerate the nucleation of the inclusions. The nucleation rate of the Mg element is relatively higher. The number of the inclusions in the adding Mg steel decrease more slowly relative to the adding Ca steel with the extension of the steelmaking time.

Effect of Calcium and Magnesium Addition on the Cast Microstructure Grain Size of HSLA Steel

A kind of HSLA steel is designed in this experiment. The thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding calcium and magnesium into the steel in the form of Si-Ca alloy and Mg-Zr alloy, respectively. The effect of calcium and magnesium addition on the cast microstructure grain size of HSLA steel was analysed. The grain size of the cast microstructure in each sample was measured by the metalloscope observation method. The results show that a large amount of oxides generated from the adding Ca and Mg elements into the steel can accelerate the nucleation and refrain the grain growth, so the grains are refined. In the process of improving temperature, the oxides of Ca and Mg elements located in the interior of austenite can accelerate the nucleation and impede the grain growth. Almost every grain becomes finer after adding Ca and Mg elements. When adding 5wt% Mg, the mean grain size is the smallest, 0.712 mm, while the biggest grain size is 1.115mm in raw steel. The grain size in Mg 5wt% steel is refined by 36.1% in contrast with the raw steel. According to the adding amounts of Ca and Mg elements in experimental steel, the range of the mean grain size is from 0.712 mm to 0.975 mm.

Effect of Doping Cerium Oxide on Microwave Absorbing Properties of Polyaniline/Al-Alloy Foams Composite Materials

To study the effect of doping cerium oxide on the microwave absorbing properties of Polyaniline /Al-alloy foams, the surface of Al-alloy foams was coated with Polyaniline (denoted by CfP),and doping 1%, 2%,5% (mass percent) cerium oxide (denoted by CfP1,CfP2,CfP5) of Polyaniline respectively. The coated Al-alloy foams were tested according to the Standard GJB 2038-94 Method to test the reflectivity of radar absorbing materials, i.e., the RCS (radar cross-section) method. The morphology and distribution of microwave absorbent were analyzed by scanning electron microscopy (SEM) and X-Ray Diffractomer (XRD).The absorbing properties of each example under different wave band were discussed. The results indicated that in the 12~18GHz and 26.5~40GHz bands the absorbing properties increase with the increase of frequency, and after doping the rare earth oxide, the absorbability of the composite material was enhanced.

Effect of Nanocalcium Oxide Addition on the Cast Microstructure of Pipeline Steel

This experiment takes the X80 pipeline steel as the research object, the thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding nanocalcium oxide into the steel with the method of carrier dispersion addition. The effect of nanocalcium oxide addition on the cast microstructure of X80 pipeline steel was analysed. The results show that the cast microstructure is consist of the ferrite and a small amount bainite. And the bainite is distributed at the boundary of the ferrite grains. When adding 0.02 wt% nanocalcium oxides, there is more bainite in the microstructure by contrast. The number of the acicular ferrite significantly increases in the cast microstructure, and the grains become more fine and uniform. Simultaneously, the granular bainite is uniformly distributed at the grain boundary and edge of the ferrite.

Effect of Nanometer Magnesium Oxide Addition on the Cast Microstructure of X80 Pipeline Steel

The pipeline steel as an application in pipeline construction must have good comprehensive mechanical properties due to the harsh environment of the pipeline engineering. So this experiment takes the X80 pipeline steel as the research object, the thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding nanomagnesium oxide into the steel with the method of carrier dispersion addition. The effect of nanometer magnesium oxide addition on the cast microstructure of X80 pipeline steel was analysed. The results show that the cast microstructure is consist of the ferrite and a small amount bainite. And the bainite is distributed at the boundary of the ferrite grains. When adding 0.02 wt% nanometer magnesium oxides, the number of bainite increases significantly in the cast microstructure, which is mostly distributed at the boundary of the ferrite grains.