Creep and dislocation substructure

Abstract

The elevated-temperature creep of pure metals and class II solid-solution alloys is reviewed with particular reference to dislocation-climb controlled creep. The phenomenological relationship between externally controlled variables such as stress and temperature are discussed in the context of easily measurable microstructural parameters such as grain size, crystal structure, and diffusivity. The role played by more subtle substructural parameters, e.g. dislocation density, distribution of dislocations inside subgrains and in subboundaries, interaction between dislocation networks, effect of stacking-fault energy, and dependence of subgrain misorientation angle on strain are emphasized. The currently available models of dislocation creep that specifically emphasize the substructural evolution during creep are reviewed. Finally, the effect of thermomechanical processing in altering the microstructure and the concomittant changes in creep properties are discussed and illustrated with recent creep data on pure Mo and a Mo-5W alloy.