Exhaustion mechanisms in the Preyield domain of niobium single crystals at low temperatures

Pure niobium single crystals were tested by tension and by stress-relaxation at stresses below the macroscopic yield stress and at temperatures between 4.2 and 70 K. The slope of the stress-strain curve and the amount of stress relaxation were investigated as a function of the nature and density of dislocations initially present in the sample. In the preyield domain the dislocation mobility was found to be governed by a thermally activated phenomenon associated to an exhaustion mechanism. This behaviour was quantitatively discussed in a model, in which edge dislocations undergo fragmentation, when the stress increases, as a result of their interaction with interstitial impurities.

[1]  P. Feltham,et al.  Microplasticity in b.c.c. metals , 1975 .

[2]  P. Kubin.  Description de la préplasticité par la théorie des phénomènes thermiquement activés , 1974 .

[3]  T. Mitchell,et al.  Dislocation relaxation in single crystals of molybdenum , 1974 .

[4]  P. Kubin,et al.  Etude de la déformation plastique de monocristaux de niobium de haute pureté a basse température , 1973 .

[5]  D. Hay,et al.  Effect of plastic prestrain on microstrain behavior of 〈100〉 and 〈110〉 TA single crystals , 1971 .

[6]  P. Groh,et al.  Stress relaxation and creep in α-iron filamentary single crystals at low temperature , 1971 .

[7]  H. Solomon,et al.  Solute effects in micro and macroyielding of iron at low temperatures , 1971 .

[8]  H. Mecking,et al.  A new aspect of the theory of flow stress of metals , 1970 .

[9]  F. G. Wilson,et al.  Interpretation of microflow measurements in niobium crystals , 1970 .

[10]  A. Luft,et al.  Electron Microscopic Investigation of the Dislocation Structure in Molybdenum Single Crystals Deformed in Tension at 293 and 493 °K , 1970 .

[11]  A. Argon,et al.  Physics of Strength and Plasticity , 1969 .

[12]  B. Escaig.  L'activation thermique des déviations sous faibles contraintes dans les structures h.c. et c.c. Par , 1968 .

[13]  D. Vesely.  The Study of Deformation of Thin Foils of Mo under the Electron Microscope , 1968 .

[14]  U. F. Kocks.  A statistical theory of flow stress and work-hardening , 1966 .

[15]  P. L. Pratt,et al.  Stress Relaxation and the Plastic Deformation of Solids , 1964 .

[16]  R. Fleischer.  Rapid Solution Hardening, Dislocation Mobility, and the Flow Stress of Crystals , 1962 .

[17]  N. Brown,et al.  Temperature dependence of the yield points in iron , 1962 .

[18]  R. Fleischer,et al.  Solution hardening by tetragonal dist ortions: Application to irradiation hardening in F.C.C. crystals , 1962 .