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diffusional creep

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Published: 01 January 1997
Fig. 29 Diffusional creep results from a higher vacancy concentration in regions of a material that experience a tensile stress compared to regions that do not. This results in a vacancy flux from the former to the latter areas, and a mass flux in the opposite direction. This extends More
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0004020
EISBN: 978-1-62708-185-6
..., followed by the models of constitutive behavior. It provides a discussion on creep mechanisms involving dislocation and diffusional flow, such as the Nabarro-Herring creep and the Coble creep. The equations for the several creep rates are also presented. Research on the mechanism of the superplastic flow...
Book Chapter

By Sammy Tin
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005404
EISBN: 978-1-62708-196-2
..., diffusional creep, twinning during creep deformation, and deformation mechanism maps. It discusses the creep-strengthening mechanisms for most structural engineering components. The article provides a description of the microstructural modeling of creep in engineering alloys. creep deformation...
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005433
EISBN: 978-1-62708-196-2
... and accommodation by dislocations. Diffusional Accommodation Models During the later part of 1960s, there were attempts to explain region II in Fig. 1 (the superplastic regime) using diffusional creep models ( Ref 18 , 19 ). Both Nabarro-Herring ( Ref 20 , 21 ) and Coble creep ( Ref 22 ) were also...
Series: ASM Handbook
Volume: 14B
Publisher: ASM International
Published: 01 January 2006
DOI: 10.31399/asm.hb.v14b.a0005183
EISBN: 978-1-62708-186-3
... creep mechanisms that are useful for illustrating the strong stress dependence of dislocation and diffusional flow. ambient temperature Isothermal constitutive modeling physical models strain hardening strain-rate-sensitive flow superplastic flow CONSTITUTIVE RELATIONS for metalworking...
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.a0003287
EISBN: 978-1-62708-176-4
... of stress and temperature for a given material. Accordingly, the stress and temperature dependencies of the creep rate can be used to identify the relevant creep mechanisms. Diffusional Creep Mechanistically, diffusional creep leads to deformation of grains when the transport of atomic vacancies...
Image
Published: 01 December 2009
Fig. 8 Schematic showing the flow of atoms from compressive boundaries to tensile boundaries during diffusional Nabarro-Herring creep. Vacancy flow occurs in the direction opposite to that of the atom flow. More
Image
Published: 01 December 1998
Fig. 45 Deformation-mechanism maps for (a) thoria-dispersed nickel and (b) type 316 stainless steel. Diffusional flow is a type of creep that occurs at very high temperatures and very low stresses. More
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.a0003288
EISBN: 978-1-62708-176-4
... ). Fortunately, all these mechanisms can be fitted into two basic categories: diffusional creep and dislocation creep. In diffusional creep, diffusion of single atoms or ions either by bulk transport (Nabarro-Herring creep) or by grain-boundary transport (Coble creep) leads to a Newtonian viscous type...
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.a0003266
EISBN: 978-1-62708-176-4
... are subject to thermally activated processes that can produce continuous plastic deformation (creep) with the application of a constant stress. For metals, various mechanisms are used to explain creep deformation, but all the mechanisms can fall into two basic categories: diffusional creep and dislocation...
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005458
EISBN: 978-1-62708-196-2
... In early theories of cavitation in metallic materials, several key ideas were developed for creep deformation and then applied to superplastic and conventional hot deformation. In these approaches, creep at low stresses and the diffusional contribution to cavity enlargement were considered the most...
Series: ASM Handbook
Volume: 20
Publisher: ASM International
Published: 01 January 1997
DOI: 10.31399/asm.hb.v20.a0002460
EISBN: 978-1-62708-194-8
Series: ASM Handbook
Volume: 22B
Publisher: ASM International
Published: 01 November 2010
DOI: 10.31399/asm.hb.v22b.a0005512
EISBN: 978-1-62708-197-9
... the yield stress of the material, and that subsequently, bonding continues by various diffusional processes (including creep). The next qualitative model was proposed by King and Owczarksi ( Ref 4 ), who suggested that bonding takes place in three stages. The first two stages were as described...
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005425
EISBN: 978-1-62708-196-2
... transformations based on classical nucleation theory and diffusional growth, and grain growth, among others, in the 1940s to1960s. Beginning in the 1980s, the incorporation of the fundamental concepts of thermodynamics and thermal physics (due to, for example, Gibbs, Ising, and others) led to a great expansion...
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005606
EISBN: 978-1-62708-174-0
... contact: limited to a few asperities (room temperature). (b) First stage: deformation of surface asperities by plastic flow and creep. (c) Second stage: grain-boundary diffusion of atoms to the voids and grain-boundary migration. (d) Third stage: volume diffusion of atoms to the voids During...
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001350
EISBN: 978-1-62708-173-3
... bonding process. (a) Initial contact: limited to a few asperities (room temperature). (b) First stage: deformation of surface asperities by plastic flow and creep. (c) Second stage: grain boundary diffusion of atoms to the voids and grain boundary migration. (d) Third stage: volume diffusion of atoms...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003546
EISBN: 978-1-62708-180-1
..., during straight and level flight, aircraft jet engines have essentially constant temperatures and imposed loads, where steady-state creep (and the environment) are the primary damage mechanisms. During takeoff and landing, however, the transient demand for more power output induces load and temperature...
Series: ASM Handbook
Volume: 14B
Publisher: ASM International
Published: 01 January 2006
DOI: 10.31399/asm.hb.v14b.a0005147
EISBN: 978-1-62708-186-3
... and strain rate, the value of the m -peak is typically in the range of 0.7 to 0.9 and increases with decreasing grain size. The value of m also exhibits a maximum as a function of temperature. The effects of grain size and temperature are closely tied to the diffusional creep contribution during...
Series: ASM Handbook
Volume: 19
Publisher: ASM International
Published: 01 January 1996
DOI: 10.31399/asm.hb.v19.a0002410
EISBN: 978-1-62708-193-1
... Abstract This article discusses fracture, fatigue, and creep of nickel-base superalloys with additional emphasis on directionally solidified and single-crystal applications. It analyzes the physical metallurgy of these alloys. The effects of grain boundary and grain size on failure...
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.a0003292
EISBN: 978-1-62708-176-4
... Abstract Studies on mechanical behavior of superplasticity at or above 50" of the melting point lead to the understanding of superplasticity as a creep phenomenon. This article provides a discussion on the four relationships that define the basic deformation characteristics associated...