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Self-consistent Constitutive Modeling of the Creep Damage Behaviour of Nickel-base Directionally Solidified Superalloys with Different Grain Orientations
Zhufeng YUE,Zhenzhou LU,

材料科学技术学报 , 1998,
Abstract: A self consistent creep damage constitutive model is developed for nickel-base directionally solidified superalloys. Grain degradation and grain boundary voiding are considered. The model parameters are determined from the creep test data of single crystal and directionally solidified superalloy with a special grain orientation. The numerical analysis shows that the model creep damage behaviours of nickel-base directionally solidified superalloys with difFerent grain orientations are in good agreement with the experimental data.
ON THE STRENGTHENING OF NICKEL-BASE SUPERALLOYS

YEN MING-KAO,CHEN HSUEH-YING,

金属学报 , 1964,
Abstract: A general review of the strengthening characteristics of the nickel-base superalloys and a primary study of principles of alloying of nickel were described. Three types of strengthening mechanisms of nickel-base alloys: solution-hardening, precipitation-hardening, and grain-boundary hardening, are discussed.
SPRAY FORMED NICKEL-BASE SUPERALLOYS
Z Li,SF Tian,XG Zhao,ZK Liang,LP Ren,GFMi,MG Yan,
Z. Li
,S.F. Tian,X.G. Zhao,Z.K. Liang,L.P. Ren,G.F.Mi and M.G. Yan

金属学报(英文版) , 1996,
Abstract: In this paper,part of the research and development work in the field of spray formed superalloys at BIAM of China is briefly summarized. With an experimental spray forming facility,whose melting capacity is suitable for making disk and columnar shaped integral-dense and clean Ni-base superalloy preforms with low oxygen content,fine grain, uniform chemistry and improved forgeability, a series of Ni-base superalloys have been spray atomized and deposited, among which three alloys have been chosen for microstructural and mechanical properties evaluation.
Segregation-induced changes in grain boundary cohesion and embrittlement in binary alloys  [PDF]
Michael A. Gibson,Christopher A. Schuh
Physics , 2015, DOI: 10.1016/j.actamat.2015.05.004
Abstract: Grain boundary embrittlement occurs when a solute enriches at a grain boundary and lowers its cohesive energy. While grain boundary enrichment is often attributed to equilibrium segregation effects, most models of embrittlement consider either the energetics of decohesion or the equilibrium adsorption at the boundary, but not both phenomena together. We develop a model for the change in cohesive energy of a grain boundary of a pure metal upon introduction of solute under conditions of equilibrium segregation prior to fracture. A heuristic grain boundary cohesion map is presented to delineate whether a given solute-solvent pair will exhibit weakening or strengthening of grain boundaries. The analysis helps to clarify that grain boundary embrittlement requires a solute that will both lower the cohesive energy of the boundary and segregate to it in the first place. The map reasonably captures known metal-metal embrittling pairs.
THE FORMATION OF ZIGZAG GRAIN BOUNDARY IN WROUGHT Ni-BASE SUPERALLOYS

YE Ruizeng,XU Zhichao,GE Zhanying,GAO Liang Beijing University of Iron,Steel Technology,YU Tongfeng,ZHANG Rungang,LI Lijia,ZHANG Peihuan Xingdu Machine Works,

金属学报 , 1985,
Abstract:
PROPERTIES OF YTTRALUMINIZING COATING ON Ni-BASE SUPERALLOYS
WANG Fuhui LO U Hanyi BAI Linxiang Institute of Corrosion,Protection of Metals,Academia Sinica,Shenyang,China WANG Fuhui,Institute of Corrosion,Protection of Metals,Academia Sinica,Shenyang,China,
WANG Fuhui LO U Hanyi BAI Linxiang Institute of Corrosion and Protection of Metals
,Academia Sinica,Shenyang,China WANG Fuhui,Institute of Corrosion and Protection of Metals,Academia Sinica,Shenyang,China

金属学报(英文版) , 1990,
Abstract: The yttraluminizing coating on the Ni-base superalloys has been developed by dipping thespecimens in a specially made yttrium-containing slurry as an underlayer and over spraying aCr-Al slurry as a protective layer,then heating to 1060℃ and holding for 1 h under argonatmosphere.Analysis by EPMA showed that the yttrium was concentrated in the intermediatezone of the coating as metallic compound Ni-5Y.After exposure to air up to 1000℃,theoxidation test revealed that the anti-oxidation resistance of the yttraluminizing coating withpost-aluminizing is much superior to that with single aluminizing only.
FATIGUE CRACK PROPAGATION OF Ni-BASE SUPERALLOYS
XBLiu,LZMa,KMChang,EBarbero,
X.B.Liu
,L.Z.Ma,K.M.Chang,E.Barbero

金属学报(英文版) , 2005,
Abstract: Time-dependent Fatigue Crack Propagation (FCP) behaviors of five Ni-base superalloys were investigated at various temperatures under fatigue with various holding times and sustained loading conditions.The new concept of damage zone is defined and employed to evaluate the alloys' resistance to hold-time FCP.A special testing procedure is designed to get the maximum damage zone of the alloys.Udimet 720 and Waspaloy show shorter damage zones than alloys 706 and 718.The fractographical analyses show that the fracture surfaces of the specimens under hold-time fatigue conditions are mixtures with intergranular and transgranular modes.As the extension of holding time per cycle, the portion of intergranular fracture increases.The effects of loading stress intensity, temperature, holding time, alloy chemistry, and alloy microstructure on damage zone and the crack growth behaviors are studied.Hold-time usually increases the alloy's FCP rate, but there are few exemptions.For instance, the steady state hold-time FCP rate of Waspaloy at 760℃ is lower than that without hold-time.The beneficial effect of hold-time was attributed to the creep caused stress relaxation during the hold-time.
Structural and chemical embrittlement of grain boundaries by impurities: a general theory and first principles calculations for copper  [PDF]
A. Y. Lozovoi,A. T. Paxton,M. W. Finnis
Physics , 2006, DOI: 10.1103/PhysRevB.74.155416
Abstract: First principles calculations of the Sigma 5 (310)[001] symmetric tilt grain boundary in Cu with Bi, Na, and Ag substitutional impurities provide evidence that in the phenomenon of Bi embrittlement of Cu grain boundaries electronic effects do not play a major role; on the contrary, the embrittlement is mostly a structural or "size" effect. Na is predicted to be nearly as good an embrittler as Bi, whereas Ag does not embrittle the boundary in agreement with experiment. While we reject the prevailing view that "electronic" effects (i.e., charge transfer) are responsible for embrittlement, we do not exclude the role of chemistry. However numerical results show a striking equivalence between the alkali metal Na and the semi metal Bi, small differences being accounted for by their contrasting "size" and "softness" (defined here). In order to separate structural and chemical effects unambiguously if not uniquely, we model the embrittlement process by taking the system of grain boundary and free surfaces through a sequence of precisely defined gedanken processes; each of these representing a putative mechanism. We thereby identify three mechanisms of embrittlement by substitutional impurities, two of which survive in the case of embrittlement or cohesion enhancement by interstitials. Two of the three are purely structural and the third contains both structural and chemical elements that by their very nature cannot be further unravelled. We are able to take the systems we study through each of these stages by explicit computer simulations and assess the contribution of each to the nett reduction in intergranular cohesion. The conclusion we reach is that embrittlement by both Bi and Na is almost exclusively structural in origin; that is, the embrittlement is a size effect.
EFFECT OF Bi SEGREGATION ON GRAIN BOUNDARY EMBRITTLEMENT OF Cu BICRYSTALS WITH [001] SYMMETRICAL TILT BOUNDARIES
Bi偏聚对[001]对称倾侧Cu双晶晶界脆性的影响

LI Guanghai,ZHANG Lide,
李广海
,张立德

金属学报 , 1995,
Abstract: The effect of Bi segregation at grain boundary on the fracture behaviour and grain boundary embrittlement was studied by using orientationcontrolled Cu bicrystals with 001] symmetrical tilt boundary.The results indicate that the fracture behaviour and fracture stress of Cu-Bi bicrystals depend strongly on the misorientation, and the grain boundary embrittlement is not related to the density of coincidence site lattice of the grain boundary but to the unsegregated grain boundary energy. the higher the grain boundary energy- the stronger the grain boundary embrittlement. The dependence could be explained by considering the boundary-dependent segregation of Bi atoms.
SEGREGATION OF ALLOYING ELEMENTS IN CAST Ni-BASE SUPERALLOYS
QIU Yiming ZHU Yaoxiao Institute of Metal Research,Academia Sinica,Shenyang,China Professor,Institute of Metal Research,Academia Sinica,Shenyang,China,
QIU Yiming ZHU Yaoxiao Institute of Metal Research
,Academia Sinica,Shenyang,China Professor,Institute of Metal Research,Academia Sinica,Shenyang,China

金属学报(英文版) , 1989,
Abstract: An investigation was made on the possibility of using Ni-x phase diagrams to judge the sym- bol and degree of segregation of alloying element x in cast nickel-base superalloys.The pre- diction coincides with the experimental data.
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