OBSERVATIONS ON HIGH TEMPERATURE CREEP PROCESSES OF A NICKEL BASE ALLOY BY TRANSMISSION ELECTRON MICROSCOPY

Abstract Nicrofer 7520 is a high temperature creep resistant nickel-base alloy with good scaling resistance to 2000 deg F (1100 deg C). Many applications are in the aerospace industry. The alloy is sometimes called alloy 75. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-496. Producer or source: VDM Technologies Corporation.

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Dislocation Mechanisms during High Temperature Creep Experiments on MC2 Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.278.7 ◽

2011 ◽

Vol 278 ◽

pp. 7-12 ◽

Cited By ~ 4

Author(s):

Fabienne Touratier ◽

Bernard Viguier ◽

Christophe Siret ◽

Sandrine Lesterlin ◽

Eric Andrieu

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

High Temperature ◽

Creep Rate ◽

Applied Load ◽

Creep Behaviour ◽

High Temperature Creep ◽

Simple Diffusion ◽

Transmission Electron ◽

Schmid Factor

The creep behaviour of MC2 single crystal superalloy has been studied at 1150°C/80 MPa, with an applied load along [001] axis. The resulting dislocation microstructures were examined by transmission electron microscopy. The occurrence of a[010] type dislocations (with a zero Schmid factor) within the ordered γ' precipitates is often observed. It is shown that those dislocations moved by a climb process, based on a mechanism involving two dislocation systems and vacancy exchanges, as proposed in the literature. We calculate the vacancy fluxes associated with such a mechanism and show that the vacancy transportation can be easily insured by a simple diffusion process. This calculation shows that the diffusion and climbing steps do not seem to be the creep rate controlling mechanisms for those situations in MC2 alloy.

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Friction stress and recovery during high-temperature creep: interpretation of creep transients following a stress reduction

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1980.0080 ◽

1980 ◽

Vol 371 (1745) ◽

pp. 279-294 ◽

Cited By ~ 21

Keyword(s):

High Temperature ◽

Stress Reduction ◽

Dislocation Substructure ◽

Base Alloy ◽

Friction Stress ◽

Objective Method ◽

High Temperature Creep ◽

Nickel Base Alloy ◽

Transient Behaviour ◽

Nickel Base

A model based on the concept of recovery-controlled creep is developed to describe the transient behaviour following a reduction in stress at high temperature. This leads to an explicit expression relating an incubation period of zero creep At to the initial, reduced and friction stresses. The creep transients in an experimental nickel-base alloy indicate that deformation is limited by the rate of growth of the dislocation substructure, and least squares analysis shows the experimental data to be compatible with the predictions of the model, which provides an objective method of measuring the friction stress. The results indicate unambiguously the existence of a finite friction stress.

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