Retardation of cyclic indentation creep exhibited in metal alloys

Abstract

Depth penetration per cycle and its retardation exhibited in specimens of 6061 Al were studied. By holding the maximum load reached during loading prior to cyclic oscillating, the creep could be effectively attenuated from the cyclic indentation. Constant depth penetration of sub-nanometers per cycle was found. The interrupt segments with different amplitudes (over- and underloading) or frequencies (frequency increasing and decreasing), but with same mean load, induced immediate retardations of cyclic indentation. As the interrupt segments have more than 10 cycles, the retardation is enhanced with the increase of cycle number. Accumulation of strain hardening due to stress concentration under the indenter tip is proposed to be the mechanism by which interrupt oscillation retards subsequent cyclic indentation.