Internal Friction and Creep-Recovery in Indium

Using low-stress pseudoshear deformation, we measured the ambient-temperaturecreep-recovery behavior of polycrystalline indium. The &+J 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-stressdiagrams 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 z2 and .c3 (in seconds): (1) 11, 123; (2) 10, 132; (3) 12, 154. Thus, z, is nearly stress independent, and .c2 increases with increasing stress. Laplaceantransformation of our ~ ( t ) measurements to get the retardation-time distribution function g(In z) indicates in all three regions a strong peak near .c2 = 3 s and a weaker, broader peak near 23 = 150 s. These agree surprisingly well with the Burgers dashpot-spring-model results. We analyzed the recovery part of the strain ~ ( t ) to obtain e-lcf) curves.