Ductility of an aluminum–4.4 wt. pct. magnesium alloy at warm- and hot-working temperatures

Abstract

An AA5182 aluminum alloy sheet, containing 4.4 wt. pct. magnesium, was subjected to tensile testing at temperatures from 100 to 400 ° C under strain rates from 1 0 − 3 up to 3 × 1 0 − 2 s −1. Flow stress, tensile elongation and reduction-in-area were measured and are correlated with deformation and fracture mechanisms. At slow strain rates and elevated temperatures, solute-drag creep produces large tensile elongations, up to 247%, and large reductions in area, up to 91%. Tensile elongation is greatest when the Zener–Hollomon parameter is in the range of 1 0 9 to 1 0 10 s −1. Ductility decreases at the slowest strain rates and highest temperatures because of cavity interlinkage leading to fracture. As strain rate increases and temperature decreases beyond the range of peak ductility, an increased rate of flow localization, i.e. necking, reduces elongation and reduction-in-area. Ductility further decreases with increasing strain rate and decreasing temperature as deformation transitions into logarithmic creep and fracture transitions to a ductile shear mode. At the lowest temperature and fastest strain rate applied, the Portevin–Le Chatelier (PLC) effect is observed and ductility is least.