Flow localization and plastic instability during the tensile deformation of Al alloy sheet

The plastic instability and necking behavior of AA8079 aluminum alloy sheet has been investigated in temper-annealed and fully annealed conditions. The approach taken was largely phenomenological; the description of the instability was based on macroscopic material properties, such as total elongation, strain-hardening, and strain-rate hardening exponents. A decrease in ductility resulting from strain localization was observed for the materials in the temper-annealed conditions. For the high-temperature annealed materials, however, necking occurred after significant plastic deformation. The relationship between post-uniform deformation, as a measure of diffuse necking, and material formability indexes (m and n) was established.