J.L. Su
,
G.K. Hu
金属学报(英文版)
An analytical micromechanical method is proposed to examine the dependence of plastic deformation on the microstructure for a PST crystal. The sub-domain microstructure of the γ phase and the effect of the α2 phase are taken into account by a proper micromechanical formulation, the dislocation slip and twinning deformation mechanisms are considered in the context of crystal plasticity. The model can well predict the dependence of stress-strain relations on loading angle with respect to the microstructure. The influence of the twinning and lamellar spacing on the deformation behavior and biaxial yield surfaces for PST crystals are also examined.
关键词:
TiAl alloy
,
null
,
null
Surface & Coatings Technology
A K38G superalloy nanocrystalline coating was produced by magnetron sputtering deposition and its transient oxides formation in the early stage of oxidation (from 5 to 1200 min) was characterized by SEM, XRD, TEM and Photo Stimulated Luminescence Spectroscopy (PSLS). During this early period of oxidation, a series phase transformation occurred and the metastable theta-Al2O3 finally transformed to stable alpha-Al2O3. The features of the transient theta-Al2O3 were detected by PSLS, XRD and TEM. The results indicate that transient alumina formation can not be avoided even with the nanocrystalline structure and the formation of these metastable alumina may contribute to the exclusive alpha-Al2O3 development on nanocrystalline materials. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
nanocrystalline coating;oxidation;PSLS;TEM;oxidation behavior;high-temperature;alloys;resistance;scale
Oxidation of Metals
The hot-corrosion behavior of a nanocrystalline coating of K38G alloy, prepared by magnetron sputtering and cast K38G in molten 75 wt.% Na2SO4+25 wt.% K2SO4 at 900degreesC was studied. The coating eliminated internal sulfidation during the early stage of corrosion as a result of the formation of a continuous and compact Al2O3 scale. The nanocrystallization of K38G alloy prolonged the incubation of breakaway corrosion and improved the corrosion resistance of K38G. The relevant corrosion mechanism is discussed.
关键词:
K38G alloy;sputtering;coating;molten sulfate;corrosion;superalloy;oxidation
周轶群
,
佟文伟
,
刘芳
,
张开阔
材料工程
doi:10.3969/j.issn.1001-4381.2014.01.004
研究了涂覆热障涂层的K417G合金800℃下由应变控制的高温低周疲劳行为,并对其循环应力-应变数据和应变-疲劳寿命数据进行了分析,给出了涂覆热障涂层K417G合金的高温应变疲劳参数.结果表明:K417G合金无涂层和涂覆热障涂层状态下的低周疲劳均属于应力疲劳,以弹性损伤为主;总应变幅较大时,涂覆热障涂层的K417G合金低周疲劳寿命稍优于无涂层的K417G合金.疲劳试样断口的微观分析表明:热障涂层对K417G合金低周疲劳裂纹萌生方式无明显影响;疲劳裂纹通常萌生于疲劳试样的表面或近表面,表现为穿晶扩展.
关键词:
热障涂层
,
K417G合金
,
弹性损伤
,
低周疲劳行为
,
过渡疲劳寿命
Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences
The formulas of the g-factors g(parallel to), g(perpendicular to) and the hyperfine structure constants A(parallel to), A(perpendicular to) for 3d(7) ions in tetragonal octathedral crystals are established from a cluster approach. Differing from previous formulas, in these formulas the role of configuration interaction (CI)- and covalency (CO)-effects is considered, and the parameters related to both effects are obtained from the optical spectra and the structural parameters of the studied crystal. From these formulas, the EPR parameters g(i) and A(i) for K2ZnF4:Co2+ are calculated. The results show good agreement with the observed values. The contributions to the EPR parameters g(i) and A(i) from the CI and CO effects, and the relationship between the sign of Delta g (=g(perpendicular to)-g(parallel to)) and the tetragonal distortion (elongated or compressed) of the ligand octahedron are discussed.
关键词:
superposition model;crystals;ions;resonance;fluorides;centers;mn2+;cr3+
稀土学报(英文版)
The oxidation behavior (isothermal and cyclic oxidation) of cast superalloy K38G and the effect of Ce+ ion implantation with dose of 1 x 10(17) ions/cm(2) upon its oxidation resistance at 900 and 1000 degrees C in air were investigated. Meanwhile, the influence of Ce+ implantation on oxidation behavior of K38G with pre-oxide scale at 1000 degrees C in air was compared. The pre-oxidation was performed at 1000 degrees C in static air for 0.25 and 1.5 h, respectively. It is shown that the homogeneous external mixture oxide of rutile TiO2 + Cr2O3 and non-continuous internal oxide of Al2O3 are formed during the oxidation procedure in all the cases. The isothermal oxidation resistance and the cracking or spallation resistance of superalloy K38G implanted with Ce+ by both of the two different implantation ways are not improved notably. This may be attributed to the mixed oxide composition characteristics and the blocking effect differences of Ce+ segregation along the oxide grain boundaries on the transport process for different diffusing ions.
关键词:
high temperature oxidation;oxidation resistance;ion implantation;superalloy K38G;rare earths;grain-boundary segregation;tial-based intermetallics;reactive;elements;cr metal;temperature;yttrium;cr2o3;behavior
于萍
,
王亚权
腐蚀学报（英文）
研究了添加0.1mass%稀土Y的铸造K38G高温合金在1000℃的恒温氧化行为.结果表明,较之不含Y的合金，含Y铸态K38G合金的氧化速率显著降低； 氧化时形成双层的外氧化膜，表层为以Cr2O3和TiO.2为主的混合氧化物层，内层为连续的Al2O3层；没有内氧化和内氮化，没有氧化膜的剥落，加入稀土Y有效地提高了氧化膜的粘附性能.
关键词:
高温氧化
,
null
,
null
,
null
Thin Solid Films
The SiO(2)-Al(2)O(3)-ZrO(2)-CaO-ZnO glass-ceramic composite coatings (GC), nanocrystalline NiCoCrAlY coating, and their combinations (bi-layer GC/NiCoCrAlY) were prepared on K38G specimens. The thicknesses of the glass-ceramic coatings and the NiCoCrAlY coatings were about 10 mu m and 20 mu m, respectively. Cyclic oxidation tests were carried out at 1100 degrees C for 120 cycles. Microstructures of the specimens before and after oxidation tests were characterized by SEM, EDS and XRD. The glass-ceramic coatings with or without a NiCoCrAlY intermediate layer improved the isothermal and cyclic oxidation resistance of the Ni-base superalloy K38G at 1100 degrees C, and performed better than the NiCoCrAlY coatings. An alumina layer formed at the glass/metal interfaces of the specimens coated by the glass-ceramic coatings with or without a NiCoCrAlY intermediate layer. The NiCoCrAlY intermediate layer was beneficial to the cyclic oxidation resistance of the glass-ceramic coatings. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Glass-ceramic coating;NiCoCrAlY;Cyclic oxidation;Magnetron sputtering;resistance;microstructure;scales
