Effect of pulse current density on creep ageing behavior of 2195 Al-Li alloy

Abstract

Electrical pulse-assisted creep ageing forming can effectively improve the mechanical properties and forming efficiency of large aluminum components. However, it is difficult to achieve uniform and consistent current density at different positions in complex components. Thus, the creep behavior, mechanical properties, and microstructure evolution of 2195 Al-Li alloy under three pulse current densities (0A/mm2, 3A/mm2 and 8A/mm2) was systematically studied. The experimental results showed that the creep deformation increases with increasing current density during the 1st hour stage of electric pulse-assisted creep ageing process. However, the total creep strain of 8 h shows a trend of decreasing and then increasing. Low density pulsed currents (non-thermal effect) can promote the precipitation of the T1 phases and θ′ phases, and narrow the precipitates free zone compared to conventional creep aged sample (0A/mm2). High density (Both of non-thermal effect and Joule heating effect) pulsed currents can promote the precipitation of T1 phases, inhibit θ′ phases and form the precipitated phase penetrate the grain boundaries. A gratifying finding is that an increase in current density accelerates the aging hardening process, but the peak strength after creep ageing is the same for different current densities. This indicates that high pulse current density can improve creep ageing forming efficiency and ageing hardening process, and can use non-uniform current densities to solve the problem of significant differences in overall structural component formability while maintaining final performance consistency.