The Role of Interfaces in Ni-Base Superalloys

Copley, S. M.; Kear, B. H.; VerSnyder, F. L.

doi:10.1007/978-1-4757-0178-4_11

Cited by 18 publications

(32 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These findings are similar to that observed in Mar-M200, containing about 60 vol pct of coherent c¢, wherein at 20°C and 760°C, at strain rates that do not influence flow stress, tensile deformation occurs through diffusionless shearing of c¢ precipitates by a/2 110 h i dislocation pairs. [29,30] Similar observations have been made on IN738LC, [31] Rene 95, [32,33] and KM4. [33] The TEM micrograph in Figure 7(a) from a specimen strained at 750°C at 10 -5 s -1 reveals randomly distributed tangles of dislocations in contrast to those in Figures 6(a), 6(b), and 7(b).…”

Section: Yield Strengthsupporting

confidence: 83%

“…The temperature at which the flow stress of c¢ reaches the peak depends on its composition, which has considerable solubility for other elements present in the alloy, [28] as well as its orientation with the stressing direction. [26] The softening of c¢ together with the monotonically reducing strength of c matrix at higher temperatures leads to the rapid decrease in yield strength at temperatures above 650°C (0.61T m ) (Figure 3(a)). …”

Section: Yield Strengthmentioning

confidence: 97%

“…[24] The dislocation interactions leading to the formation of sessile ''KearWilsdorf locks,'' when a dislocation from c matrix enters a c¢ precipitate, and the consequent anomalous increase in flow stress with temperature are well addressed in the literature. [25][26][27] The temperature independence of the yield strength of the alloy until about 600°C is therefore the net effect of the reduction in strength of c phase compensated by the increase in strength of c¢ precipitates. Sufficient thermal activation to overcome such locks through diffusional processes is thought to become available only at elevated temperatures that release the locked dislocation segments and make them glissile, resulting in softening of c¢.…”

Section: Yield Strengthmentioning

confidence: 99%

See 2 more Smart Citations

Tensile Properties of Ni-Based Superalloy 720Li: Temperature and Strain Rate Effects

Gopinath

Gogia

Kamat

et al. 2008

Metall Mater Trans A

View full text Add to dashboard Cite

Tensile properties, deformation, and fracture behavior of a wrought nickel-base superalloy 720Li have been studied in standard solutionized and two-stage-aged condition in the temperature range of 25°C to 750°C. Effect of strain rate on tensile behavior was assessed at 25°C, 400°C, and 750°C at five strain rates that range between 10 -5 s -1 and 10 -1 s -1 . The yield strength and ultimate tensile strength of the alloy remained unaffected by temperature until about 600°C and 500°C, respectively, typical of superalloys strengthened by fine and coherent intermetallic Ni 3 Al-based precipitates. The flow stress of the alloy was found to be insensitive to the strain rates studied at 25°C and 400°C. However, at 750°C, the flow stresses showed strain rate sensitivity at strain rates <10 -3 s -1 . The strain hardening behavior at 25°C and 400°C were similar. At 750°C, stain hardening was observed only at strain rates >10 -3 s -1 , and at lower strain rates, tensile instability was seen to set in immediately after yielding. The alloy exhibited ductile dimple fracture at all the temperatures and strain rates studied. Microstructural investigations indicate that in regimes where flow stresses are insensitive to strain rate, deformation occurs through heterogeneous planar slip, whereas in strain rate sensitive regimes, thermally activated diffusion processes promote homogeneous deformation.

show abstract

Section: Yield Strengthsupporting

confidence: 83%

Section: Yield Strengthmentioning

confidence: 97%

Section: Yield Strengthmentioning

confidence: 99%

See 1 more Smart Citation

Tensile Properties of Ni-Based Superalloy 720Li: Temperature and Strain Rate Effects

Gopinath

Gogia

Kamat

et al. 2008

Metall Mater Trans A

View full text Add to dashboard Cite

show abstract

“…9. The -c .... value (41.4 MPa) was obtained from the data [31] on MarM-200 single crystals. The experimental data belong to a variety of alloys which differ intrinsically in terms of varying degrees of strengthening due to y' and Y" predicates.…”

Section: Ni-base Alloysmentioning

confidence: 99%

A theoretical model for roughness induced crack closure

Ravichandran

1990

Int J Fract

View full text Add to dashboard Cite

A theoretical model for the effects of grain size on the magnitude of roughness induced crack closure (RICC) at fatigue crack growth threshold has been proposed. With the basic configuration of a crack propagating incrementally along planar slip bands and deflecting at grain boundaries, an idealized zig-zag crack path is considered. The effective slip band length is considered to be equal to grain size. It is assumed that the dislocations emitted from the crack tip upon loading to form the pile-up are completely irreversible to produce a combined mode I and mode II displacement at the crack tip. The assumption of continuously distributed dislocations in the pile-up facilitated the calculation of crack tip sliding displacement (CTSD) along the slip plane from which the mode I closure disregistry just behind the crack tip can be calculated. The closure stress intensity factor at threshold, Kcl,t h could then be expressed as a function of critical resolved shear stress, average macroscopic yield stress, angle subtended by the slip plane with the crack plane and the length of the slip band. Comparisons of the predicted trends with experimental data from various alloy systems indicate good agreement. NomenclaturePICC = Plasticity induced crack closure U = OICC = Oxide induced crack closure RICC = Roughness induced crack closure U~, U u = AK~h = Alternating stress intensity range at 0 = threshold hk/ Tcrss = Kcl,t h = Closure stress intensity level at threshold r 0 = K,~ax = Maximum stress intensity factor in a fatigue cycle ~l(x), q(x') = Dislocation distribution functions CTOD = z,, = Applied shear stress CTSD = b = Burger's vector E = G = Shear modulus a~. = v = Poisson's ratio 6,n~x = 1 = Length of the slip band or pile-up 6~ = N = Number of dislocations in the pile-up d =

show abstract

“…As the stress increases within the matrix channels due to the high dislocation density, dislocation pairs become able to move into and cut c¢ precipitates. [53][54][55][56][57][58][59] Therefore, it can be assumed that thermally activated dislocation annihilation and diffusion-controlled processes such as interfacial pinning at dispersoids and circumvention of c¢ particles by dislocations take over only at relatively high temperatures and low creep rates for PM 3030. In addition, thermal instability of c¢ precipitates becomes more and more important as temperature further increases and load further decreases, resulting in a reduced contribution of c¢ particles to the restriction of dislocation motion.…”

Section: Particle Strengthening Contributionmentioning

confidence: 99%

Creep Behavior and Damage of Ni-Base Superalloys PM 1000 and PM 3030

Nganbe

Heilmaier

2009

Metall Mater Trans A

View full text Add to dashboard Cite

Two oxide dispersion strengthening (ODS) nickel-base superalloys, a solely dispersionstrengthened alloy (PM 1000) and an additionally c¢-strengthened alloy (PM 3030) are investigated regarding creep resistance at temperatures between 600°C and 1000°C. The creep strength advantage of PM 3030 over PM 1000 decreases as the temperature increases due to the thermal instability of the c¢ phase. The particle strengthening contribution in both alloys increases linearly with load. However, solid solution softening leads to an apparent drop in particle strengthening in PM 1000. Deformation concentration in slip bands is more accentuated in PM 3030-R34 due to additional c¢ strengthening combined with strongly textured coarse and elongated grain structure. Finer, equiaxed grains reduce creep strength at higher temperatures due to grain boundary deformation processes and premature pore formation, but have only minor impact at low and intermediate temperatures.

show abstract

The Role of Interfaces in Ni-Base Superalloys

Cited by 18 publications

References 3 publications

Tensile Properties of Ni-Based Superalloy 720Li: Temperature and Strain Rate Effects

Tensile Properties of Ni-Based Superalloy 720Li: Temperature and Strain Rate Effects

A theoretical model for roughness induced crack closure

Creep Behavior and Damage of Ni-Base Superalloys PM 1000 and PM 3030

Contact Info

Product

Resources

About