DEPENDENCE OF TRANSIENT AND STEADY-STATE CREEP ON GRAIN-SIZE IN AGED AL-10WT-PERCENT-ZN ALLOY

The effect of grain size as well as ageing temperature on the creep ch aracteristics of Al-10 wt% Zn alloy have been studied. It has been fou nd that the steady state creep rate epsilon over dot decreases by incr easing grain size, whereas it increases by increasing ageing temperatu re. It is suggested that the decrease of epsilon over dot may be due t o the change in the density of mobile dislocations in addition to the change in concentration of point defects and impurity atmospheres. An empirical formula epsilon over dot = ml(-2) + c has been proposed to c orrelate the creep rate and grain size. The values of the activation e nergies controlling the creep processes corresponded to that required for dislocation glide.