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Effect of current and atomized grain size distribution on the solidification of Plasma Transferred Arc coatings
Bond, Danielle;D'Oliveira, Ana Sofia Clímaco Monteiro;
Materials Research , 2012, DOI: 10.1590/S1516-14392012005000101
Abstract: plasma transferred arc (pta) is the only thermal spray process that results in a metallurgical bond, being frequently described as a hardfacing process. the superior properties of coatings have been related to the fine microstructures obtained, which are finer than those processed under similar heat input with welding techniques using wire feedstock. this observation suggests that the atomized feedstock plays a role on the solidification of coatings. in this study a model for the role of the powders grains in the solidification of pta coatings is put forward and discussed. an experiment was setup to discuss the model which involved the deposition of an atomized co-based alloy with different grain size distributions and deposition currents. x ray diffraction showed that there were no phase changes due to the processing parameters. microstructure analysis by laser confocal microscopy, dilution with the substrate steel and vickers microhardness were used the characterized coatings and enriched the discussion confirming the role of the powdered feedstock on the solidification of coatings.
Liquid-liquid Phase Transformation Kinetics of an Atomized Al-Pb Alloy Drop

ZHAO Jiuzhou,GAO Lingling,HE Jie,WANG Jiangtao,CHEN Guiyun,

金属学报 , 2006,
Abstract: High pressure gas atomization experiments have been carried out with Al-Pb immiscible alloy. Powders containing fine Pb dispersions have been obtained. A model describing the microstructure evolution in a rapidly solidified atomized droplet was developed. The model takes into account of the common effects of the nucleation, the diffusional growth of the minority phase droplets, the collisions and coagulations between the minority phase droplets and spatial phase separation. The formation of the microstructure of the atomized droplets was calculated. It was demonstrated that the calculated results have a good coincidence with the experimental ones. The solidification process of the atomized A1-Pb alloy drop was discussed in details.

WANG Xiaofeng,ZHAO Jiuzhou,He Jie,WANG Jiangtao,

金属学报 , 2005,
Abstract: Based on the population dynamic method a model has been developed to describe the solidification process and the thermal histories of gas-atomized droplets. The model is coupled with the droplets' heat transfer controlling equation and the droplets' motion controlling equation, and used in Cu-13.5%Sn (mass fraction) alloy. The effects of the droplet size, the initial gas velocity, the superheat of the melt and the wetting angle between the primary phase and the catalyzing substrate for heterogeneous nucleation on droplet solidification behaviors were discussed.
Spray Atomized and Codeposited Al-Li Based Metal-matrix Composites Processing and Properties
E Raskin,S Nayim,MPolak,JBaramANSembira,

材料科学技术学报 , 1995,
Abstract: In spray atomization and codeposition, a molten stream of metal is disintegrated into a fine dispersion of droplets by high velocity gas jets. The resulting semi-solidified droplets are directed towards a substrate where they impact and collect as rapidly solidified splats. Relatively high rates of solidification are achieved as a result of the thinness of the splats and the rapid heat extraction during flight and upon impacting with the substrate. The processing method uses codeposition of the metallic semi-solidified droplets (metallic matrix) with the injected reinforcement ceramic particles. In the present paper, the microstructures, mechanical properties, interfacial properties, thermal stability and aging behaviour of spray atomized and codeposited Al-Li-X MMC's (injected X=SiC, Al2O3) are reported and correlated to the processing conditions.
Fabrication of ZrC/SiC, ZrO2/SiC and ZrO2 powders by carbothermal reduction of ZrSiO4  [PDF]
Ljiljana Kljajevi?,Branko Matovi?,Sne?ana Nenadovi?,Zvezdana Ba??arevi?
Processing and Application of Ceramics , 2011,
Abstract: The zirconia/silicon carbide (ZrO2 /SiC) and ZrO2 powders are prepared by carbothermal reduction of natural mineral zircon (ZrSiO4). The zircon powder was mixed with activated carbon as a reducing agent and heattreated in a controlled flow atmosphere of Ar. Phase evolution and phase content were followed as a function of temperature (1573–1973 K) and C/ZrSiO4 ratio (C/ZrSiO4 = 1, 4, 5 and 7), by means of ex-situ X-ray diffraction and SEM/EDS analysis. By varying the temperature and C/ZrSiO4 ratio, different powder compositions were obtained (m-ZrO2; m-ZrO2/c-ZrO2; c-ZrO2; c-ZrO2/SiC).
Solidification of Cu-Co ally under rapid cooling conditions

ZHAO Jiuzhou,LI Haili,HE Jie,ZHANG Xianfei,

金属学报 , 2008,
Abstract: Gas atomization experiments are carried out with Cu-20wt%Co alloy. Powders with a fine dispersion of the Co-rich particles are obtained. A model has been developed to describe the solidification process of the atomized drops. The kinetic details of the microstructure evolution in the drops are calculated. It is indicated that the numerical results have a good accordance with the experimental ones. The microstructure development during the liquid-liquid decomposition is a result of the concurrent action of the nucleation, the growth of the minority phase droplets, the collision coagulations between the droplets and the spatial separation of phases. A bigger drop achieves a lower cooling rate and a lower nucleation rate of the minority phase droplets. It exhibits, therefore, a coarse Co-rich particle microstructure.
Co-Dispersion Behavior of ZrB2–SiC–B4C–C Powders with Polyethyleneimine  [PDF]
Jie Yin,Jian Chen,Xuejian Liu,Hui Zhang,Yongjie Yan,Zhengren Huang,Dongliang Jiang
Materials , 2013, DOI: 10.3390/ma6094249
Abstract: The aqueous dispersion behavior of ZrB 2, SiC powders with B 4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface was measured by thermal gravimetric (TG) analysis. Rheological measurements displayed the effect of dispersant on the flow behavior of as-prepared slurries. An optimum condition was obtained with 1 wt % PEI. The viscosity of 40 vol % ZrB 2–SiC–B 4C–C (ZSBC) suspension at 100 s ?1 was as low as 0.74 Pa·s, which was suitable for aqueous processing.
Solidification microstructure of 3D--meshy SiC/Cu metal matrix composites

XING Hongwei CAO Xiaoming HU Wanping ZHAO Longzhi ZHANG Jinsong,

材料研究学报 , 2004,
Abstract: 3D-meshy SiC/Cu metal matrix composite was fabricated by squeeze casting process. The influence of process conditions on solidification microstructure of the composites was studied. The results showed that 3D-meshy SiC ceramic skeleton played an important role during the solidification of the matrix and the course of crystal growth and crystallization. Under the certain conditions, the dendrites perpendicular to skeleton surface appeared, and the fine and even equiaxed grains structure formed. The influence of skeleton apertures on microstructure was very remarkable. The fine apertures were benefit to grain refining and structure uniformity, while big apertures were apt to produce macroscopic segregation and concentration of plumbum. The tin inverse segregation was lightened for the SiC skeleton, because tin was gathered in a very narrow region near the surface of skeleton, which avoided tin mass segregation in the surface layer of the cast.
Modeling and Simulation of the Microstructure Evolution of the Gas-atomized Alloy Droplets during Spray Forming
Jiuzhou ZHAO,Dongming LIU,Hengqiang YE,

材料科学技术学报 , 2003,
Abstract: In order to understand the solidification process of an atomized droplet and predict the fraction solidification of droplets with flight distance during spray forming, a numerical model based on the population dynamics approach is developed to describe the microstructure evolution under the common action of the nucleation and growth of grains. The model is coupled with droplets heat transfer controlling equations and solved for AI-4.5 wt pct Cu alloy. It is demonstrated that the numerical results describe the solidification process well.
Preparation and Characterization of Cu Coated SiC Composite Powders by in-situ Chemical Deposition  [PDF]
SHI Jin-Gang, YAO Hui, CHEN Ming-Hai, LIU Ning, LI Qing-Wen
无机材料学报 , 2012, DOI: 10.3724/sp.j.1077.2012.11575
Abstract: A facile one-step in-situ chemical deposition method was introduced to synthesize Cu-Coated SiC composite powders, using [Cu(NH3)4]2+ ions as copper source and N2H4·H2O as reductant, respectively. Scanning electronic microscope (SEM), X-Ray diffraction (XRD), Fourier transform infrared spectroscope (FT-IR) and Zeta potential were used to investigate the structure, morphology and composition of the prepared core/shell composite powders. The corresponding formation mechanism was proposed based on the comparative study. It is revealed that the SiO2 film on the surfaces of pre-oxidated SiC particles can effectively enhance the adsorption of [Cu(NH3)4]2+ ions toward the negatively charged surface, which is favorable to the following in-situ reduction by N2H4·H2O around SiC particles. Nearly continuous Cu coating can be formed by changing the reaction process. The concentration of [Cu (NH3)4]2+ ions and reaction temperature affect the reaction rate and coating structure. The process parameters are optimized to obtain the best coating structure with [Cu(NH3)4]2+ ions concentration of 0.2 mol/L and reaction temperature of 70 respectively.
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