Internal Friction and Creep-Recovery in Indium

Using low-stress pseudoshear deformation, we measured the ambient-temperature creep-recovery behavior of polycrystalline indium. The ε-σ diagram shows three regions with increasing stress : stress exponents of 1.05, 7.4, and 2.0. The diagram resembles remarkably the dislocation-velocity-shear-stress diagrams reported for various materials by many authors, who interpreted the diagrams by dislocation dynamics. Applying an extended Burgers model (two Kelvin-Voigt elements) gave for the three regions the following relaxation times τ2 and τ3 (in seconds) : (1) 11, 123 ; (2) 10, 132 ; (3) 12, 154. Thus, τ1 is nearly stress independent, and τ2 increases with increasing stress. Laplacean transformation of our ε(t) measurements to get the retardation-time distribution function g(ln τ) indicates in all three regions a strong peak near τ2=3s and a weaker, broader peak near τ3=150s. These agree surprisingly well with the Burgers dashpot-spring-model results. We analyzed the recovery part of the strain ε(t) obtain Q-1(f) curves