Superplasticity-like creep behavior of coarse grained ternary Al alloys

Abstract: Enhanced tensile ductilities in coarse grained Al-Mg-Zn and Al-Mg-Fe materials were studied. The materials were Al-2Mg-5Zn, Al-3Mg-5Zn, Al-4Mg-5Zn, Al-3Mg-0.11Fe, Al-3Mg-0.27Fe, and Al-3Mg-0.40Fe. Tensile elongation-to-failure tests were conducted at constant cross-head speed and constant temperatures from 300 to 450 ℃. Strain rate change tests were conducted at a constant temperature from 300 to 450 ℃ and in strain-rate range from 4.31×10−5 to 1.97×10−2 s−1. Experimental results show that over 100 % ductilities are consistently achieved in these materials. This superplasticity-like behavior is rate-controlled by solute-drag creep. Although ternary Zn and Fe additions do not have an adverse effect on solute-drag creep and ductility, they increase stress exponent and its sensitivity to Mg content during solute-drag creep. Key words: Al-Mg alloys; superplasticity; solute-drag creep; tensile ductility; strain-rate sensitivit