Influence of copper solute of the creep rate sensitivities of aluminium

The presence of Cu atoms as continuous networks at the grain boundaries of an Al--Cu alloy does not prevent the moving of dislocations during creep (or at least partially). The dislocations can be absorbed by these boundaries and penetrate through them. That leads to changes of shape and structure of grains and also to the sliding of grains against each other. This was deduced from the accelerating increase in the sensitivity of the steady state creep rate to the applied stress of an Al--2.8 wt.% Cu alloy examined at wide range of temperatures (50-350 deg C) and applied stresses (7-10 MPa). This raid increase in the sensitivity parameter of the steady state creep rate occurs in Al--Cu alloys at quite higher ranges of applied stresses and may be attributed mainly to the contribution of the grain boundary movements to the creep strain.