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Wu X.,University of Science and Technology Beijing | Guo Z.,University of Science and Technology Beijing | Guo L.,Rensselaer Polytechnic Institute | Yang F.,University of Science and Technology Beijing | And 2 more authors.
Xiyou Jinshu/Chinese Journal of Rare Metals

NiMo-TiC cermet coating was sprayed by the detonation gun spray system on stainless steel matrix with different oxygen-fuel ratios. The oxygen-fuel ratio in relation to the coating hardness and phase composition and the oxidation behavior of the elements in spraying process were studied. The hardness and the porosity were tested by the coating cross-section metallographic method. The phase composition and the micro-structure were analyzed with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the hardness of the coating cross-section was about HV0.3 850, and the porosity was closed to 1%. When the oxygen-fuel ratio reached to 1.25:1.00, the hardness decreased. Micro structure of the coating was lamellar and tightly combined with the trans-layer. But there were some unmelted TiC particles with the same dimension of the powder. XRD showed that some TiC particles were converted to TiO and Ti2O3 by oxidation process during the spray. TiO became Ti2O3 when oxygen proportion increased. The relative content of the Ti2O3 increased with the oxygen-fuel ratio increasing. Most of Mo elements were oxidized. The oxydate was gasified by exploded flame. It was found that when the oxygen- ethyne ratio was 1.1:1.0, the gas current in gun's barrel was almost the same as the theoretical detonation wave. The coating performance had preferable overall performance. Source

Xiang S.-H.,Shenyang Ligong University | Wei K.-X.,Shenyang Ligong University | Wei K.-X.,Beijing North Vehicle Group Corporation | Li S.-P.,Beijing Institute of Technology | And 4 more authors.
Tuijin Jishu/Journal of Propulsion Technology

In order to get the nearly neutral burning law, mathematical model was propesed. The variance of burning law was selected as the objective function, and the burning law for slotted tube grain was studied by the method of analytic formulae. Based on simplex method, slotted tube grain was optimized by changing the multiple design parameters at the same time. The results show that the decrease of inner diameter and slot depth can decrease the rate of the change for burning area. The increase of the arc can reduce the difficulty of slotting and the increase of slot length can decrease the rate of the change for burning area. The decrease of the amplitude for objective function can decrease the rate of the change for burning area, and can make the burning law close to neutral. Source

Xu H.,North University of China | Zhang X.,China Datang Corporation | Liu Y.,China Datang Corporation | Shi Y.,China Military Representative Office of Peoples Liberation Army Stationed in 618 Factory | And 2 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering

The mechanical properties and the corrosion mechanism of SiCp/2A50 composite materials were studied. The specimens were prepared by the liquid forging. The SiCp particles were added into a partially solidified matrix alloy. The experimental results show that the strength of SiCp/2A50 composite increases with increasing of the SiCp volume fraction, and the ductility of SiCp/2A50 composite decreases with increasing particulates size. The pitting potentials of 2A50 and SiCp/2A50 composite materials are similar. The corrosion resistance of SiCp/2A50 of the pit initiation is almost the same as that of the matrix alloy. It has been found that once pits initiate, the pitting corrosion damage is accelerated owing to the formation of crevices between the reinforcement and the matrix. The cathodic current of the SiCp/2A50 is slightly larger than that of the matrix alloy. The SiCp markedly decreases the pitting corrosion resistance of the composite and the matrix alloy in chloride containing environment. SiCp accelerates the corrosion rate of composite materials, namely the corrosion velocity of composite materials is greater than that of the aluminum alloys. Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved. Source

Cai J.,Xian University of Architecture and Technology | Wang K.,Xian University of Architecture and Technology | Han Y.,Beijing North Vehicle Group Corporation
High Temperature Materials and Processes

True stress and true strain values obtained from isothermal compression tests over a wide temperature range from 1,073 to 1,323 K and a strain rate range from 0.001 to 1 s-1 were employed to establish the constitutive equations based on Johnson Cook, modified Zerilli-Armstrong (ZA) and strain-compensated Arrhenius-type models, respectively, to predict the higherature flow behavior of Ti-6Al-4V alloy in α + β phase. Furthermore, a comparative study has been made on the capability of the three models to represent the elevated temperature flow behavior of Ti-6Al-4V alloy. Suitability of the three models was evaluated by comparing both the correlation coefficient R and the average absolute relative error (AARE). The results showed that the Johnson Cook model is inadequate to provide good description of flow behavior of Ti-6Al-4V alloy in α + β phase domain, while the predicted values of modified ZA model and the strain-compensated Arrhenius-type model could agree well with the experimental values except under some deformation conditions. Meanwhile, the modified ZA model could track the deformation behavior more accurately than other model throughout the entire temperature and strain rate range. © 2016 by De Gruyter. Source

Xu H.,North University of China | Zhang X.,Advanced Research Corp. | Wang C.,Beijing North Vehicle Group Corporation | Liu C.,Beijing North Vehicle Group Corporation | Zhang W.,Beijing North Vehicle Group Corporation
Materials Science Forum

AZ91D magnesium alloy is one of the most widely used magnesium alloys in the production of metal forming, which use the characteristics from liquid state to solid state of metal to form. The present status of the research and application of the semi-solid forming for AZ91D magnesium alloys at present was reviewed in this paper, including the microstructural characteristics, the thixotropic and rheological behavior, the forming process of semi-solid for AZ91D magnesium alloys and the mechanical properties of the parts made of semi-solid magnesium alloys. The developing prospects and the key points of the semi-solid forming for AZ91D magnesium alloys were forecasted, and the industrial application of the alloy were also discussed. © 2016 Trans Tech Publications, Switzerland. Source

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