Effects of solid solute Mn and Fe contents on creep behavior of Al–Mn alloys

The creep behavior of an Al–0.6%Mn alloy at 200°C was investigated to obtain fundamental knowledge on the metallurgical factors associated with threshold stress generation. Before creep testing, the alloy was subjected to solution treatment at 620°C for 10 h. The creep testing results confirmed the presence of threshold stress. A plausible mechanism for the threshold stress caused Mn atoms in solid solution is as follows: the atmosphere of solute Mn atoms around the moving dislocations significantly restrict the mobility of the dislocations when the loaded stress is small enough that the dislocations remain in the atmosphere of the solute Mn, since the diffusivity of Mn in the Al matrix is far smaller than that of the Al self-diffusion. The effects of Fe content on the creep behavior at 200°C were investigated using Al–0.25%Si–1.0%Mn– (0.04, 0.6) Fe alloys from the viewpoint of industrial application. Higher Fe content resulted in a reduction in the threshold stress since the amount of solute Mn decreased with increasing amount of Al– (Fe, Mn) –Si constituent particles.