3 Creep Strain vs. Time at Constant Engineering Stress
4 Creep Machine Length of specimen has increased Initial position from L0 to L1.Initial positionCreep machine with variable lever arms to ensure constant stress on specimen; note that l2 decreases as the length of the specimen increases.
11 Activation Energies for Creep Activation energies for creep (stage II) and self-diffusion for a number of metals.(Adapted with permission from O. D. Sherby and A. K. Miller, J. Eng. Mater.Technol., 101 (1979) 387.)
12 Secondary CreepRatio between activation energy for secondary creep and activation energy for bulk diffusion as a function of temperature.(Adapted with permission from O. D. Sherby and A. K. Miller, J. Eng. Mater. Technol., 101 (1979) 387.)
14 Diffusion CreepFlow of vacancies according to (a) Nabarro–Herring and (b) Coble mechanisms, resulting in an increase in the length of the specimen.
15 Dislocation Climb Dislocation climb (a) upwards, under compressive σ22 stresses, and (b) downwards, under tensile σ22 stresses.
16 Diffusion CreepDifferent regimes for diffusion creep in alumina; notice that cations (Al3+) and anions (O2−) have different diffusion coefficients, leading to different regimes of dominance.(From A. H. Chokshi and T. G. Langdon, Defect and Diffusion Forum, 66–69 (1989) 1205.)
17 Dislocation (Power Law) Creep: 10^(-2) < σ/G < 10^(-4) Power relationship between ˙ε and σ for AISI 316 stainless steel.Adapted with permission from S. N. Monteiro and T. L. da Silveira, Metalurgia-ABM, 35 (1979) 327.
18 Dislocations Overcoming Obstacles Weertman MechanismDislocation overcoming obstacles by climb, according to Weertman theory. (a) Overcoming Cottrell–Lomer locks. (b) Overcoming an obstacle.
19 Shear Stress and Shear Strain Rate Shear stress vs. shearstrain rate in an aluminum (6061) with 30 vol.% SiC particulate composite in creep.(From K.-T. Park, E. J. Lavernia, and F. A. Mohamed, Acta Met. Mater., 38 (1990) 2149.)
20 Dislocation Glide Effect of stress and temperature on deformation substructure developed in AISI 316 stainless steel in middle of stage II.Reprinted with permission from H.-J. Kestenbach, W. Krause, andT. L. da Silveira, Acta Met., 26 (1978) 661.)
21 Grain Boundary Sliding (a) Steady-stategrain-boundary sliding withdiffusional accommodations.(b) Same process as in (a), in anidealized polycrystal; the dashedlines show the flow of vacancies.(Reprinted with permission fromR. Raj and M. F. Ashby, Met. Trans.,2A (1971) 1113.)
22 Ashby-Verrall’s Model Grain-boundary sliding assisted by diffusion in Ashby–Verrall’s model.(Reprinted with permission from M. F. Ashby and R. A. Verrall, Acta Met., 21 (1973) 149.)
23 Weertman-Ashby Map for Pure Silver Weertman–Ashby map for pure silver, established for a critical strain rate of 10−8 s−1; it can be seen how the deformation-mechanism fields are affected by the grain size.Adapted with permission from M. F. Ashby, Acta Met., 20 (1972) 887.
24 Weertman-Ashby Map for Tungsten Weertman–Ashby map for tungsten, showing constant strain-rate contours.(Reprinted with permission from M. F. Ashby, Acta Met., 20 (1972) 887.)
26 Mechanisms of intergranular nucleation .(From W.D. Nix and J. C. Gibeling, in Flow and Fracture at ElevatedTemperatures, ed, R. Raj (Metals Park, Ohio: ASM, 1985).)
27 Heat-Resistance Materials Transmission electron micrograph of Mar M-200; notice the cuboidal γ precipitates.(Courtesy of L. E. Murr.)
28 Microstructural Strengthening Mechanism in nickel-based superalloys (Reprinted with from C. T. Sims and W. C. Hagel, eds., The Superalloys (New York: Wiley, 1972), p. 33.)
29 RaftingRafting in MAR M-200 monocrystalline superalloy; (a) original configuration of gamma prime precipitates aligned with three orthogonal cube axes; (b) creep deformed at 1253 K for 28hours along the  direction, leading to coarsening ofprecipitates along loading direction.(From U. Glatzel, “Microstructure and Internal Strains of Undeformed and Creep Deformed Samples of a Nickel-Based Superalloy,”Habilitation Dissertation,Technische Universit¨at, Berlin,1994.)
30 Stress-Rupture (at 1000 hours) vs. Temperature for Heat Resistant MaterialsStress versus temperatures curves for rupture in1,000 hours for selected nickel-based superalloys.(Reprinted with permission from C. T. Sims and W. C. Hagel, eds., The Superalloys (New York: Wiley, 1972), p. vii.)
31 Gas Turbine Cross-section of a gas turbine showing different parts. The temperature of gases in combustion chamber reaches 1500 ◦C.
32 Turbine Blade (a) Single crystal turbine blade developed for stationary turbine. (Courtesy of U. Glatzel.) (b) Evolution ofmaximum temperature in gasturbines; notice the significant improvement made possible by theintroduction of thermal barrier coatings (TBCs).(Courtesy of V. Thien, Siemens.)
33 Creep in PolymersSpring–dashpot analogs (a) in series and (b) in parallel.
34 Maxwell and Voigt Models Strain–time and(b) stress–time predictions forMaxwell and Voigt models.
35 Viscoelastic PolymerStrain response as a function of time for a glassy, viscoelastic polymer subjected to a constant stress σ0. Increasing the molecular weight or degree of cross-linking tends to promote secondary bonding between chains and thus make the polymer more creep resistant.
36 Creep Compliances (a) A series of creep compliances vs. time, both on logarithmic scales, over a range of temperature. (b) The individual plots in (a) can be superposed by horizontal shifting (along the log-time axis) by an amount log aT, to obtain a master curve corresponding to a reference temperature Tg of the polymer. (c) Shift along the log-time scale to produce a master curve.(Courtesy of W. Knauss.)(d) “Experimentally” determinedshift factor.
37 Stress RelaxationA constant imposed strain ε0 results in a drop in stress σ(t) as a function of time.
38 Effect of Crosslinking on Stress Relaxation A master curve obtained in the case of stress relaxation, showing the variation in the reduced modulus as a function of time. Also shown is the effect of cross-linking and molecular weight.
39 ElectromigrationMetal interconnect line covered by passivation layer subjected toelectromigration;(a) overall scheme;(b) voids and cracks producedby thermal mismatch andelectromigration;(c) basic scheme used in NixArzt equation, which assumesgrain-boundary diffusion ofvacancies counterbalancingelectron wind.(Adapted from W. D. Nix and E. Arzt.Met. Trans., 23A (1992) 2007.)
40 SuperplasticitySuperplastic tensile deformation in Pb–62% Sn eutectic alloy tested at 415 K and a strain rate of 1.33 × 10−4 s−1; total strain of 48.5.(From M. M. I. Ahmed and T. G. Langdon, Met. Trans. A, 8 (1977) 1832.)
41 Plastic Deformation(a) Schematic representation of plastic deformation in tension with formation and inhibition of necking. (b) Engineering-stress– engineering-strain curves.
42 Strain Rate Dependence Strain-rate dependence of (a) stress and (b) strain-rate sensitivity for Mg–Al eutectic alloy tested at 350 ◦C (grain size 10 μm).(After D. Lee, Acta. Met., 17 (1969) 1057.)
43 Fracture Tensile fracture strain and stress as a function of strain rate for Zr–22% Al alloy with 2.5-μm grain size.(After F. A. Mohamed, M. M. I. Ahmed, and T. G. Langdon, Met. Trans. A, 8 (1977) 933.)
44 Effect of Strain Rate Sensitivity Effect of strain-rate sensitivity m on maximum tensileelongation for different alloys (Fe, Mg, Pu, Pb–Sr, Ti, Zn, Zr based).(From D. M. R. Taplin, G. L. Dunlop, and T. G. Langdon, Ann. Rev. Mater. Sci., 9 (1979) 151.)
45 Cavitation in Superplasticity Cavitation in superplasticity formed 7475-T6 aluminum alloy (ε = 3.5) at 475 ◦C and 5 × 10−4 s−1. (a) Atmospheric pressure. (b) Hydrostatic pressure P = 4 MPa. (Courtesy of A. K. Mukherjee.)
46 Effect of Grain Size on Elongation (a) Effect of grain size on elongation: (A) Initial configuration. (B) Largegrains. (C) Fine grains (10 μm) (Reprinted with permission from N. E. Paton, C. H.Hamilton, J. Wert, and M. Mahoney, J. Metal, 34 (1981) No. 8, 21.)(b) Failure strainsincrease with superimposed hydrostatic pressure (from 0 to 5.6 MPa). (Courtesy ofA. K. Mukherjee.)