ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Results are presented here of an investigation of the kinetics of high-temperature creep of mono- and polycrystalline nickel samples and of the associated substructural changes. It is shown that at low stresses, not exceeding the so-called linear creep limitp o creep takes place according to the Nabarro-Herring mechanism. The characteristic particle size allowed for in the Nabarro-Herring theory is similar to the size of the blocks (subgrains), measured by X-ray diffraction. In the first stage of creep at stressesp 〈p 0 the average block size increases and the dislocation density decreases. In the second and third stages the creep does not cause any noticeable changes in the substructural characteristics (block size, dislocation density). Creep of the material is accompanied by the onset of porosity, the formation and development of which is due, apparently, to the coalescence of vacancies. Atp 〉p 0, when Weertman's mechanism is the main creep mechanism, the dislocation density increases with increase in the amount of creep. Creep in this stress range is accompanied by the appearance of pore-cracks which are formed mainly at the grain (block) boundary junctions; these hinder the movement of dislocations. The dependence of the linear creep limit on temperature is determined by the temperature-dependence of the shear modulus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00554037
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