Solute-drag creep and tensile ductility in aluminum alloys

Solute-drag creep is an important deformation mechanism at warm-working temperatures in Al alloys containing Mg. The high strain-rate-sensitivity resulting from solute-drag creep, m = 0.3, can lead to enhanced tensile ductility, a significant benefit for the forming of complex shapes. Mechanical testing of commercial Al alloys 5754 and 5182 has produced tensile ductilities of 100% and better at temperatures of 300 degrees C and higher and initial strain rates of 10(-2) s(-1) and slower. Far lower tensile ductilities are measured for commercial alloys 7150, 6111, and 6022 and an experimental Al alloy containing 5.1 wt, pet. Zn, Al-5Zn. These differences in ductility result from the primary solute additions in each material, Mg in 5182 and 5754, Zn in 7150 and Al-5Zn, and Si in 6111 and 6022. Mg leads to solute-drag creep and high ductility while Zn and Si generally do not. The tensile ductilities of the two commercial 5000-series alloys studied do not reach those observed in low-impurity, binary AI-Mg materials, which have provided tensile ductilities of up to 325%.