Effect of grain size on cyclic creep behaviour in a commercially pure aluminium at room temperature

Abstract

Both static creep behaviour and cyclic creep behaviour of a commercially pure aluminium with different grain sizes have been investigated at room temperature. The creep rate of both stage I and II static creep and stage I cyclic creep were drastically affected by grain size. It was found that a critical grain size existed above which the cyclic creep retardation gave way to acceleration. The threshold stress at which the cyclic creep retardation is replaced by acceleration, or vice versa, was found to be affected by impurities in the material. An intermediate amount of unloading which gave rise to the lowest cyclic creep rate was observed in the present study. The behaviour of cyclic creep acceleration and retardation was explained satisfactorily in terms of thermally activated deformation processes.