Contribution of grain boundary diffusion and capillarity forces to the diffusional creep of wires or fibers

Herring’s analysis of the Newtonian creep of wires with a bamboo grain structure is modified to include the effects of grain boundary diffusion and capillarity. The grain boundary contribution depends on the ratio σDb/2DRv whereR is the wire radius,Db andDv are the boundary and volume diffusion coefficients, and σ is the width of the grain boundary. Capillarity is introduced in a consistent fashion into the analysis and the classical result for equilibrium between the applied load and capillarity forces is found. The creep rate of single crystal fibers embedded in a plastically deformed matrix is considered for some simple geometries.