The high-temperature oxidation resistance of the nickel superalloy prepared by the laser powder bed fusion(LPBF)has been significantly increased as a result of in-situ formation of a thermal barrier layer(α-Al_(2)O_(...The high-temperature oxidation resistance of the nickel superalloy prepared by the laser powder bed fusion(LPBF)has been significantly increased as a result of in-situ formation of a thermal barrier layer(α-Al_(2)O_(3)+CaMoO4)during oxidative annealing of surface layers modified by electric spark treatment(EST).The reactive EST of the LPBF-built items based on nickel EP741NP alloy was carried out with low-melting Al−12%Si,Al−6%Ca−0.6%Si and Al−7%Ca−1%Mn electrodes.It was found that under EST done by Al−7%Ca−1%Mn electrode an intermetallic(β-NiAl+γ'-Ni3Al)15μm-thick layer reinforced by spherical oxide(CaMe)O nanoparticles was formed.Formation of that structure increases the wear resistance of LPBF nickel superalloy by 4.5 times.Further oxidative annealing at 1000°C leads to a formation of continuous two-layered coating with an inner layer ofα-Al_(2)O_(3) and an outer layer of CaMoO4,which together act as an effective barrier preventing the diffusion of oxygen into the bulk of the superalloy.展开更多
In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution ...In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.展开更多
The seasonal signal and long-term trend in the height time series of 10 IGS sites in China are investigated in this paper. The offset detection and outlier removal as well as the removal of common mode error are perfo...The seasonal signal and long-term trend in the height time series of 10 IGS sites in China are investigated in this paper. The offset detection and outlier removal as well as the removal of common mode error are performed on the raw GPS time-series data developed by the Scripps Orbit and Permanent Array Center(SOPAC). The seasonal-trend decomposition procedure based on LOESS(STL) is utilized to extract precise seasonal signals, followed by an estimation of the long-term trend with the application of maximum likelihood estimation(MLE) to the seasonally adjusted time series. The Up-compo- nents of all sites are featured by obvious seasonal variations, with significant phase and amplitude modulation on some sites. After Kendall's tau test, a significant trend(99% confidence interval) for all sites is achieved. Furthermore, the trends at sites TCMS and TNML have significant changes at epochs 2009.5384 and 2009.1493(95% confidence interval), respectively, using the Breaks For Additive Seasonal and Trend test. Finally, the velocities and their uncertainties for all sites are estimated using MLE with the white noise plus flicker noise model. And the results are analyzed and compared with those announced by SOPAC. The results obtained in this paper have a higher precision than the SOPAC results.展开更多
基金supported by the Ministry of Science and Higher Education of the Russian Federation under State Research Assignment(No.0718-2020-0034)Development Program of MISIS(No.K7-2023-009)within the Framework Strategic Academic Leadership Program"Priority-2030".
文摘The high-temperature oxidation resistance of the nickel superalloy prepared by the laser powder bed fusion(LPBF)has been significantly increased as a result of in-situ formation of a thermal barrier layer(α-Al_(2)O_(3)+CaMoO4)during oxidative annealing of surface layers modified by electric spark treatment(EST).The reactive EST of the LPBF-built items based on nickel EP741NP alloy was carried out with low-melting Al−12%Si,Al−6%Ca−0.6%Si and Al−7%Ca−1%Mn electrodes.It was found that under EST done by Al−7%Ca−1%Mn electrode an intermetallic(β-NiAl+γ'-Ni3Al)15μm-thick layer reinforced by spherical oxide(CaMe)O nanoparticles was formed.Formation of that structure increases the wear resistance of LPBF nickel superalloy by 4.5 times.Further oxidative annealing at 1000°C leads to a formation of continuous two-layered coating with an inner layer ofα-Al_(2)O_(3) and an outer layer of CaMoO4,which together act as an effective barrier preventing the diffusion of oxygen into the bulk of the superalloy.
基金Projects(51301214,51441002)supported by the National Natural Science Foundation of ChinaProject(cstc2013jcyj A50017)supported by Fundamental and Cutting-edge Research Plan of Chongqing,China+1 种基金Project supported by EPSRC LATEST2 Program,UKProject supported by Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.
基金supported by the National High Technology Research and Development Program of China(Grant No.2013AA122501-1)the National Natural Science Foundation of China(Grant Nos.41374019,41020144004,41474015,41274045,41574010)Funded by State Key Laboratory of Geo-information Engineering(Grant No.SKLGIE2015-Z-1-1)
文摘The seasonal signal and long-term trend in the height time series of 10 IGS sites in China are investigated in this paper. The offset detection and outlier removal as well as the removal of common mode error are performed on the raw GPS time-series data developed by the Scripps Orbit and Permanent Array Center(SOPAC). The seasonal-trend decomposition procedure based on LOESS(STL) is utilized to extract precise seasonal signals, followed by an estimation of the long-term trend with the application of maximum likelihood estimation(MLE) to the seasonally adjusted time series. The Up-compo- nents of all sites are featured by obvious seasonal variations, with significant phase and amplitude modulation on some sites. After Kendall's tau test, a significant trend(99% confidence interval) for all sites is achieved. Furthermore, the trends at sites TCMS and TNML have significant changes at epochs 2009.5384 and 2009.1493(95% confidence interval), respectively, using the Breaks For Additive Seasonal and Trend test. Finally, the velocities and their uncertainties for all sites are estimated using MLE with the white noise plus flicker noise model. And the results are analyzed and compared with those announced by SOPAC. The results obtained in this paper have a higher precision than the SOPAC results.
