Papers by Author: Jing Pei Xie

Abstract: The grain size of W-Cu nanocomposites would greatly affect the density of W-Cu alloy. In this work, W-Cu oxide nanocomposite powders were prepared by sodium tungstate and copper nitrate via hydrothermal method, and W-Cu nanocomposite powders were obtained by subsequently co-reduction process. The characterization of W-Cu nanocomposite powders were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), energy spectrum analysis (EDS) and transmission electron microscope (TEM). The results indicated that hydrothermal method was a good method for the preparation of W-Cu oxide nanocomposite powders. W-Cu nanocomposite powders, whose grain size was about 70nm and distributed uniformity, were manufactured by co-reduction process.

Abstract: The effects and the mechanisms of namo TiN on the high chromium cast iron are studied, the material has been prepared through infiltration casting and addition of high carbon ferrochrome powder and nano TiN powder. The alloy is formed on the surfaced of guide plate, and the wear resistance of alloy have been studied by means of SEM, XRD micro-analysis and wear-resistant performance. The grain size and the type of carbide in the organization are affected by nano TiN, and the wear resistance of carbon chromium alloy layer is affected by the type of carbide; when the addition of nano TiN is 1% (wt), the grain size is apparently refined, overeutectic primary M7C3 in the hypereutectic is precipitated uniformly in considerable amounts, therefore the wear resistance of alloy can be improved effectively.

Abstract: 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.

Abstract: The numerical simulation of temperature gradient in the solidification process for large bushing castings of zinc-base alloy was made with HUAZHU CAE/Inte-CAST10.0 software in this paper. Tendency and the position of shrinkage were predicted,and the effect of cooling water rate and cooling time on temperature gradient and shrinkage during the molten metal solidification was discussed. The results show that:seting chilled iron at bottom of bearing bush and using water-cooling metal core in inner cavity of casting simultaneously, can eliminated shrinkage hole and porosity.

Abstract: In this paper , by SEM、EDS、XRD and Shimadzu AG-I250KN precision universal testing machine , the metallurgical structure, fracture appearance, the mechanical properties of the ZA303 under high temperature were systematically studied .The results shows that :The microstructure of ZA303 at room temperature are : α phase + (α＋η) _eutectoid + ε phase + η phase. After adding modifying elements B、Ti in ZA303：the microstructure of the alloy is from gross dendrites to uniform equiaxed grains , the quantity, morphology and distribution of the (α + η) have greatly change: the quantity of (α + η) is less, from a continuous network to intermittent block, and its end become blunt, or even cylindrical horn and dispersed distribution; on the grain boundary, the size of ε phase become smaller and dispersed distribution, the number of mesh ε phase reduced but intermittent strips increased; adding B、Ti have a good effect of restraining Al element segregation，so the foundry defects decreased obviously. In the range of experimental temperature, the increase of ductility is large while the tensile strength is small: at the same time, the mechanical performances stability is better than that without modification.

Abstract: The numerical solidification simulation for gear ring steel casting has been made, and the location and reasons forming casting defects have been predicted by HUAZHU CAE software. Simulating result shows that the directional solidification and efficient feeding were maintained and the casting perfects can be realized by means of the computer simulation optimizing technological and rationally design of gating system, insulated risers, iron chill and compensating efficiently. After magnetic particle detection and ultrasonic inspection, the properties and microstructure of the Gear ring steel casting are in accord with the international standard.

Abstract: The laser welding of particle reinforced SiCp/ZC71 magnesium matrix composite was carried out using a Nd:YAG laser welding experimental system. The mechanical properties of welded joint was studied by tensile test and the morphology of tensile fracture, microstructure as well ingredient of welded joint were observed by SEM. The results show that welding technology for composites is harsher. SiC particles distributed uniformly and the white magnesium intermetallic compound dots disappeared in the laser welded seam because the precipitation of the magnesium intermetallic compounds was prohibited owing to the rapid solidification and cooling of the laser-welded seam.. There is no evident heat affect zone in the weld seams；The mechanical properties of welded joint are worse than those of matrix metal. The weld zone is the weakest part in welded joint. The much lower tensile strength of the seam compared to the tensile strength of the ZC71/SiCp substrate attributed to the surface roughness of the seams and some solidification micron-sized pores (especially between SiC particles and magnesium alloy matrix)，The fracture morphology of welded joint indicated a brittle cleavage fracture.

Abstract: This work aims to eliminate contamination of the surface of crucible with silicon carbide during fusion preparation sample of the X-ray fluorescence analysis used in relation to electroless Ni–P plating process on the surface of SiC crucible in the alkaline bath. The structure, morphology and component of the coated layers were clarified by means of XRD, SEM and EDAX. Also, the electrochemical measurements was carried out to characterize the reduction mechanism of Ni deposition. The bath compositions were nickel sulfate 20 g/L, sodium hypophosphite 30 g/L, sodium citrate 10 g/L，ammonium chloride 20 g/L, containing a mixed additives of thiourea, sodium lauryl sulfate and coumarin. The thickness of coating was 3.47 μm after plating for 15 min from this bath at 318 K. The coating is relatively dense and smooth and has a nodular surface morphology. The uniform Ni–P film is a mixture of microcrystalline of Ni₅P₄ and crystalline phases of Ni in the alkaline bath, with the components of 4.74%P and 95.26%Ni. The nickel deposition reaction occurs at -1.07 V appropriately with the peak current density of 32 mA/cm² and the electrochemical deposition of nickel is mainly controlled by the electrochemical process.

Abstract: Abstract. In this paper,the effect of rare earth La on microstructures and properties of ZA30 alloy were studied . The result shows that The structure is refined and mechanical properties are improved by adding La to ZA30 alloy,the alloy have best structures and comprehensive mechanical properties when La content is 0.1%; Rich-La phases are metallic compound Cu₂La,Al₂La and LaZn and precipitate in blocky form ,its number and size increase with La; The abrasive resistance of ZA30 alloy is significantly improved when La is over 0.3%.

Abstract: Erosion wear experiments on Nickel-Chromium cast iron were tested by MCF-30 erosion test machine. The structure and surface morphology of these samples were analyzed by Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and XRD. The influences of the impact angle and acidity on erosion wear property were analyzed. The discipline of the erosion wear property was discussed as well. The experimental results indicate that after oil quench at 960°C and temper at 250°C, the alloy carbide (Fe, Cr)₃C which works as the wear resistance skeleton distributes uniformly in the matrix ; the shape of erosion wear curve is “M”. and the biggest wear loss is when the impact angle is 60°; the erosion wear property is affected greatly by the strong acid, but is little even can be ignored when pH≥3. The erosion wear mechanism of Nickel-Chromium cast iron is selective wear.