Papers by Author: Hui Bin Xu

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Authors: Hong Li Wu, Xin Qing Zhao, Jian Xu, Chun Gen Zhou, Hui Bin Xu
Abstract: A first principle study was performed to discuss the high temperature oxidation mechanism of NiTi alloys with the special emphasis on the effect of Nb on the oxidation behavior. The calculation results suggest that the Nb atom prefers the Ti site in Ni(Ti,Nb). The addition of Nb will not only reduces the electron density of Ti-d and Ni-d states near the Fermi energy level but the their electron contributions to the p-orbital of Ti. In addition, the Nb atom increases the formation energy of the Ti defect, which will decrease the diffusion of Ti atoms. All these Nb-induced effects account for the improvement of high temperature oxidation resistance, which agrees well with the experimental results.
Authors: Fan Li, Jian Qin Mao, Hai Shan Ding, Wen Bo Zhang, Hui Bin Xu, Cheng Bao Jiang
Abstract: In this paper, a new method which combines the least square method with Tree-Structured fuzzy inference system is presented to approximate the Preisach distribution function. Firstly, by devising the input sequence and measure the output, discrete Preisach measure can be identified by the use of the least squares method. Then, the Preisach function can be obtained with Tree-Structured fuzzy inference system without any special smoothing means. So, this new method is not sensitive to noise, and is a universal approximator of the Preisach function. It collect the merit and overcome the deficiency of the existing methods.
Authors: Chun Xia Zhang, Fu Shun Liu, Sheng Kai Gong, Hui Bin Xu
Abstract: Two layer thermal barrier coatings (TBCs) were prepared by EB-PVD (Electron Beam-Physical Vapor Deposition) at different substrate temperatures in the range of 823 to 1123K, and their microstructure was investigated with SEM and AC impedance as a function of substrate temperature and thermal cycling time. YSZ layer of all TBCs samples is in column structure, but the grain size and growth orientation are different with substrate. In this research, impedance spectra (IS) was measured as a function of thermal cycling between 1323K and 298K for these thermal barrier coatings. Grain boundary and bulk can be distinguished from analysis of AC impedance spectroa to provide information about the relation between microstructure and electric properties.The change in IS until failure was found to be related with the thickness, microcracks and macrocracks of TGO and the change in the interfacial of TGO/YSZ.
Authors: Yong Wang Kang, Chun Gen Zhou, Sheng Kai Gong, Hui Bin Xu
Abstract: Al-Cu-Fe-Cr quasicrystalline coating was deposited on a substrate of stainless steel by low-pressure plasma spraying (LPPS) method. The corrosion behavior of such coating was studied by polarization in 1mol/l H2SO4 and 0.1mol/l NaOH solutions at room temperature. The polarization curve shows that LPPS Al-Cu-Fe-Cr quasicrystalline coating can turn to passive state both in 1mol/l H2SO4 solution and in 0.1mol/l NaOH solution. The corrosion resistance of the coating is poorer than that of bulk quasicrystal in 0.1mol/l NaOH solution. Moreover, in strong acid solution LPPS Al-Cu-Fe-Cr quasicrystalline coating has more corrosion resistance than 1Cr18Ni9Ti in some potential range ranging from -200mVSCE to -35mVSCE, but in strong alkaline solution the corrosion resistance of the coating is poorer than 1Cr18Ni9Ti.
Authors: Chang Liang Wang, Chun Gen Zhou, Sheng Kai Gong, Hui Bin Xu
Abstract: The cyclic oxidation of thermal barrier coating (TBC) specimens consisting of nickel-base superalloy, low pressure plasma sprayed Ni-24Cr-6Al-0.7Y (wt.%) bond coatings and air plasma sprayed 7.5 wt.% yttria stabilized zirconia top coatings was studied at 1050°C in air, (air + 5%H2O), O2 and (O2 + 5%H2O) respectively. The oxidation kinetics of the TBC in each test environment accords with parabolic law at the initial stage and obeys almost liner law at the final stage. The cyclic oxidation life of the TBC is 500h (1h/cyc) in O2 and (O2 + 5%H2O) and 900 h in air and (air + 5%H2O). The SEM observations indicated the oxide formed along the bond coat and top coat interface after failure at 1050°C in different environments are all consisted of Al2O3, Ni(Al,Cr)2O4, NiO and Cr2O3.
Authors: H.T. Zhao, Junchen Yao, Yue Ma, Hui Bin Xu
Abstract: The effect of aging treatment on the damping capacity of the high strength damping aluminum alloy prepared by RS/PM process was investigated. The damping properties of the alloy were examined with dynamic mechanic thermal analyzer (DMTA). The damping capacity, as well as the dynamic Young’s modulus was measured at different temperatures and different loading frequencies. The analysis of microstructure characteristics was performed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was found that the damping capacity of the alloy did not change significantly after aging treatment, but changed remarkably with the variation of measurement temperature and loading frequency. Grain boundaries in the alloy became clear and sharp with aging treatment proceeded and contributed to the total damping capacity.
Authors: Zhi Gang Kong, Lei Ji, Shu Suo Li, Ya Fang Han, Hui Bin Xu
Abstract: The effect of heat treatment on microstructures and stress rupture property of a Ni3Al base single crystal alloy DDIC6 was studied in the present investigate. The single crystal specimens were produced by screw selection crystal method. The heat treatment for the alloy was 1300°C/10h+1120°C/4h+870°C/32h and 1300°C/10h+870°C/32h.The microstructures were examined by SEM, TEM and X-ray EDS techniques. The stress rupture tests were carried out in air by constant load creep machines under 1100°C/130MPa with the specimens size of φ5×25 mm. The experimental results showed that the as-cast large size γ′ phases entirely dissolved after 1300°C/10h, and secondary fine γ′ phases precipitated by following aging at 1120°C and 870°C for certain periods of time. The stress rupture life under 1100°C/130MPa increased from 20~30hrs for as-cast condition to 60~100hrs for heat treatment condition. The improvement of the creep resistance of the alloy may attribute to the decrement of the elements segregation at dendrite and interdendritic areas, and the proper size and distribution of γ′ phases.
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