Creep at low stresses: An evaluation of diffusion creep and Harper-Dorn creep as viable creep mechanisms

High-temperature creep experiments often reveal a transition at very low stresses to a region where the stress exponent is reduced to a value lying typically in the range of ∼1 to 2. This region is generally associated with the occurrence of a new creep mechanism, such as grain-boundary sliding, diffusion creep, and/or Harper-Dorn creep. Several recent reports have suggested that diffusion creep and Harper-Dorn creep may not be viable creep mechanisms. This article examines these two processes and demonstrates that there is good evidence supporting the occurrence of both creep mechanisms under at least some experimental conditions.

[1]  S. Raj,et al.  Creep behavior of copper at intermediate temperatures—I. Mechanical characteristics , 1989 .

[2]  J. Wolfenstine,et al.  Diffusional Creep and Diffusion-Controlled Dislocation Creep and Their Relation to Denuded Zones in Mg-ZrH2 Materials , 1998 .

[3]  T. Langdon,et al.  An evaluation of deformation models for grain boundary sliding , 1982 .

[4]  M. E. Kassner,et al.  Restoration mechanisms in large-strain deformation of high purity aluminum at ambient temperature and the determination of the existence of “steady-state” , 1994 .

[5]  H. Jones,et al.  Microstructural evidence for diffusional creep in copper using atomic force microscopy , 2001 .

[6]  T. Langdon.  An evaluation of the strain contributed by grain boundary sliding in superplasticity , 1994 .

[7]  D. A. Smith,et al.  Comment on “refutation of the relationship between denuded zones and diffusional creep” , 1994 .

[8]  W. Vickers,et al.  DIFFUSION-CREEP IN MAGNESIUM ALLOYS. , 1967 .

[9]  I. Crossland,et al.  Microstructural observations on specimens deformed by diffusion creep , 1975 .

[10]  R. C. Gifkins,et al.  Grain-boundary sliding during diffusional creep , 1975 .

[11]  J. Wolfenstine,et al.  Refutation of the relationship between denuded zones and diffusional creep , 1993 .

[12]  E. N. da C. Andrade,et al.  Über das zähe Fließen in Metallen und verwandte Erscheinungen = On the viscous flow in metals, and allied phenomena , 1910 .

[13]  Terence G. Langdon,et al.  Identifiying creep mechanisms at low stresses , 2000 .

[14]  Robert L. Coble,et al.  A Model for Boundary Diffusion Controlled Creep in Polycrystalline Materials , 1963 .

[15]  J. E. Dorn,et al.  VISCOUS CREEP OF ALUMINUM NEAR ITS MELTING TEMPERATURE. Technical Report No. 48 , 1957 .

[16]  G. W. Greenwood.  Denuded zones and diffusional creep , 1994 .

[17]  David A. Miller,et al.  An investigation of harper-dorn creep—I. Mechanical and microstructural characteristics , 1982 .

[18]  Alan A. Johnson.  Stage III recovery in group VA body-centered cubic transition metals , 1973 .

[19]  Conyers Herring,et al.  Diffusional Viscosity of a Polycrystalline Solid , 1950 .

[20]  J. Wolfenstine,et al.  Evidence for Nabarro-Herring creep in metals: fiction or reality? , 1993 .

[21]  J. E. Harris.  The Inhibition of Diffusion Creep by Precipitates , 1973 .

[22]  Byung‐Nam Kim,et al.  Contribution of grain boundary sliding in diffusional creep , 2000 .

[23]  G. S. Murty,et al.  Uncertainty in separating the strain contributions of sliding and diffusion in diffusional creep , 2001 .

[24]  W. Blum,et al.  Harper-Dorn Creep — a Myth? , 1999 .

[25]  T. Langdon,et al.  The role of matrix dislocations in the superplastic deformation of a copper alloy , 1986 .

[26]  B. Burton,et al.  In defense of diffusional creep , 1995 .

[27]  Terence G. Langdon,et al.  Deformation mechanism maps for superplastic materials , 1976 .

[28]  R. Valiev,et al.  An investigation of the role of intragranular dislocation strain in the superplastic Pb-62% Sn eutectic alloy , 1993 .

[29]  F. Mohamed,et al.  On the nature and origin of Harper-Dorn creep , 1982 .

[30]  N. Mott,et al.  Report of a Conference on Strength of Solids , 1948 .

[31]  F. Mohamed,et al.  Effect of impurity content on superplastic flow in the Zn-22% Al alloy , 1988 .

[32]  W. Cannon.  The contribution of grain boundary sliding to axial strain during diffusion creep , 1972 .

[33]  C. John.  The effect of crack loading mode on stress-corrosion cracking , 1975 .

[34]  F. Mohamed,et al.  Superplastic deformation behavior in commercial and high purity Zn- 22 Pct Al , 1988, Metallurgical and Materials Transactions A.

[35]  T. Langdon,et al.  The transition from dislocation climb to viscous glide in creep of solid solution alloys , 1974 .

[36]  P. Phillips.  The Slow Stretch in Indiarubber, Glass, and Metal Wires when subjected to a Constant Pull , 1903 .

[37]  C. Sellars,et al.  Recrystallization during creep of nickel , 1966 .

[38]  T. Langdon,et al.  An examination of the breakdown in creep by viscous glide in solid solution alloys at high stress levels , 1982 .

[39]  J. E. Dorn,et al.  Creep of aluminum under extremely small stresses , 1958 .

[40]  H. Yamagata.  Dynamic recrystallization and dynamic recovery in pure aluminum at 583K , 1995 .

[41]  T. Langdon.  A method of distinguishing between diffusion creep and harper-dorn creep at low stress levels , 1996 .

[42]  E. Andrade.  The Flow in Metals under Large Constant Stresses , 1914 .

[43]  T. Langdon,et al.  Creep and substructure formation in an Al-5% Mg solid solution alloy , 1981 .

[44]  T. Langdon.  A unified approach to grain boundary sliding in creep and superplasticity , 1994 .

[45]  R. C. Gifkins,et al.  Grain-Boundary Sliding and Axial Strain during Diffusional Creep , 1975 .

[46]  F. Nabarro.  Harper‐Dorn Creep – A Legend Attenuated? , 2000 .

[47]  M. E. Kassner,et al.  Dynamic grain growth a restoration mechanism in 99.999 Al , 1993 .

[48]  F. Mohamed,et al.  An investigation of Harper–Dorn creep at large strains , 2001 .

[49]  R. C. Gifkins,et al.  Grain boundary displacements due to diffusional creep , 1970 .