Crystallographic Orientation and Spatially Resolved Damage in a Dispersion-Hardened Al Alloy

Abstract

Damage of an Al alloy was in-situ monitored employing neutron diffraction. It is evidenced in (1) the increase of the magnitude of lattice strain while decreasing the applied load and (2) a quick drop of the lattice strain during unloading from tension. Indeed, the studied sample finally failed during unloading from the tensile phase of a tension-compression cyclic loading. After failure, the maximum tensile type residual lattice strain was in the <111> grains in a direction at ~39° with respect to the loading direction (LD). The maximum compressive one is nearly parallel with the LD. Micro voids tend to concentrate along the central axis and two big ones lie at the lines ~39° off the LD. The full-field elasto-viscoplastic finite element model suggests that the relatively hard <422> and <111> grains were damaged more than the <311> and <200> grains. The measured elastic constants of the former reduced ~17% after three stages of loading. The banded structure triggered by the hard particles is one source of damage. It is more obvious in the relatively hard <111>, <422> and <311> grains than in the softest <200> grains. The band structure in the <111> grains is also ~39° tilted from the LD.

Keywords: Necking, Damage, Residual lattice strain, Neutron diffraction, Banded structure