Galvanic, compatibility between graphite epoxy composite materials (GECM) and LY12CZ aluminum alloy was evaluated in different atmospheric corrosion environments and by laboratory electrochemical measurements. Open ci...Galvanic, compatibility between graphite epoxy composite materials (GECM) and LY12CZ aluminum alloy was evaluated in different atmospheric corrosion environments and by laboratory electrochemical measurements. Open circuit potential electrochemical measurements showed a relatively large potential difference about 1 volt between the GECM and LY12CZ aluminum alloy, and this difference provided the driving force for galvanic corrosion of the LY12CZ aluminum alloy as an anode. Having been exposed for 1, 3 or 5 years in Beijing, Tuandao and Wanning station, GECM/LY12CZ couples showed significant losses of strength and elongation. Protective coatings and non-conductive barriers breaking the galvanic corrosion circuit were evaluated under the same atmospheric corrosive conditions. Epoxy primer paint, glass cloth barriers and LY12CZ anodizing were effective in galvanic corrosion control for GECM/LY12CZ couples.展开更多
The effects of process parameters on the microstructural evolution, includinggrain size and volume traction of the a phase during hot forming of a TC6 alloy were investigatedusing compression tests. Experiments were c...The effects of process parameters on the microstructural evolution, includinggrain size and volume traction of the a phase during hot forming of a TC6 alloy were investigatedusing compression tests. Experiments were conducted on the material with (α + β) phases atdeformation temperatures of 800, 860, 920, and 950℃, strain rates of 0.001, 0.01, 1, and 50 s^(-1),and height direction reductions of 30%, 40%, and 50%. After reaching a peak value near 920℃, thegrain size and volume fraction decrease with further increase of deformation temperature. The strainrate affects the morphologies and grain size of α phase of the TC6 titanium alloy. At a lowerstrain rate, the effect of the strain rate on the volume fraction is greater than that at a higherstrain rate under the experimental conditions. The effects of the strain rate on the microstructurealso result from deformation heating. The grain size of the α phase increases with an increase inheight direction reduction after an early drop. The effect of height direction reduction on thevolume fraction is similar to that of the grain size. All of the optical micrographs andquantitative metallography show that deformation process parameters affect the microstructure duringhot forming of the TC6 alloy, and a correlation between the temperature, strain, and strain rateappears to be a significant fuzzy characteristic.展开更多
This article investigated effects of degrees of deformation, heat treatment temperatures and holding times on the recrystallization behavior of directionally solidified DZ4 superalloy. The results showed that, recryst...This article investigated effects of degrees of deformation, heat treatment temperatures and holding times on the recrystallization behavior of directionally solidified DZ4 superalloy. The results showed that, recrystallization of DZ4 superalloy could take place during solution heat treatment after certain degrees of cold work and depths of recrystallization increased with increasing degrees of deformation and heat treatment temperature. At the temperature below y’ solvus, prolonged holding times did not play an important role in improving recrystallization depths. Moreover, prevention measures for recrystallization of directionally solidified blades were given.展开更多
A 3 kW radio frequency (RF) magnetron-sputtering unit was used to producezirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlYbond coat layer by cathodic arc deposition. The ...A 3 kW radio frequency (RF) magnetron-sputtering unit was used to producezirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlYbond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and theresidual stress in the bond coat layer and the effects of heat treatment on the residual stress arepresented. After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the wholedepth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz)decreases from 16.4 to 3.3 mu m. The microstructure and phase composition of the coatings wereinvestigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results showthat the/ NiCrAlY bond coat is composed of gamma and Cr phases, and the A1_2O_3 scales are formednear the interface between the ZrO_2 ceramic layer and the NiCrAlY bond coat. No degradationoccurred to RF sputtered ceramic coatings after oxidating at 1150 deg C for 100 h, heating at 1150deg C for 5 min and then air-cooling for 500 thermal cycles.展开更多
基金The authors gratefully acknowledge the financial support from National Key Basic Research and Development Programme of China (No. G1999065004).
文摘Galvanic, compatibility between graphite epoxy composite materials (GECM) and LY12CZ aluminum alloy was evaluated in different atmospheric corrosion environments and by laboratory electrochemical measurements. Open circuit potential electrochemical measurements showed a relatively large potential difference about 1 volt between the GECM and LY12CZ aluminum alloy, and this difference provided the driving force for galvanic corrosion of the LY12CZ aluminum alloy as an anode. Having been exposed for 1, 3 or 5 years in Beijing, Tuandao and Wanning station, GECM/LY12CZ couples showed significant losses of strength and elongation. Protective coatings and non-conductive barriers breaking the galvanic corrosion circuit were evaluated under the same atmospheric corrosive conditions. Epoxy primer paint, glass cloth barriers and LY12CZ anodizing were effective in galvanic corrosion control for GECM/LY12CZ couples.
基金This work was financially supported by the Ministry of Science and Technology (No. G2000067206)the Teaching and Research Award Fund for Outstanding Young Teachers in Higher Education Institutions of MOE, China
文摘The effects of process parameters on the microstructural evolution, includinggrain size and volume traction of the a phase during hot forming of a TC6 alloy were investigatedusing compression tests. Experiments were conducted on the material with (α + β) phases atdeformation temperatures of 800, 860, 920, and 950℃, strain rates of 0.001, 0.01, 1, and 50 s^(-1),and height direction reductions of 30%, 40%, and 50%. After reaching a peak value near 920℃, thegrain size and volume fraction decrease with further increase of deformation temperature. The strainrate affects the morphologies and grain size of α phase of the TC6 titanium alloy. At a lowerstrain rate, the effect of the strain rate on the volume fraction is greater than that at a higherstrain rate under the experimental conditions. The effects of the strain rate on the microstructurealso result from deformation heating. The grain size of the α phase increases with an increase inheight direction reduction after an early drop. The effect of height direction reduction on thevolume fraction is similar to that of the grain size. All of the optical micrographs andquantitative metallography show that deformation process parameters affect the microstructure duringhot forming of the TC6 alloy, and a correlation between the temperature, strain, and strain rateappears to be a significant fuzzy characteristic.
文摘This article investigated effects of degrees of deformation, heat treatment temperatures and holding times on the recrystallization behavior of directionally solidified DZ4 superalloy. The results showed that, recrystallization of DZ4 superalloy could take place during solution heat treatment after certain degrees of cold work and depths of recrystallization increased with increasing degrees of deformation and heat treatment temperature. At the temperature below y’ solvus, prolonged holding times did not play an important role in improving recrystallization depths. Moreover, prevention measures for recrystallization of directionally solidified blades were given.
文摘A 3 kW radio frequency (RF) magnetron-sputtering unit was used to producezirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlYbond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and theresidual stress in the bond coat layer and the effects of heat treatment on the residual stress arepresented. After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the wholedepth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz)decreases from 16.4 to 3.3 mu m. The microstructure and phase composition of the coatings wereinvestigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results showthat the/ NiCrAlY bond coat is composed of gamma and Cr phases, and the A1_2O_3 scales are formednear the interface between the ZrO_2 ceramic layer and the NiCrAlY bond coat. No degradationoccurred to RF sputtered ceramic coatings after oxidating at 1150 deg C for 100 h, heating at 1150deg C for 5 min and then air-cooling for 500 thermal cycles.
