Plastic anisotropy and tension-compression asymmetry in nanotwinned Al–Fe alloys: An in-situ micromechanical investigation

Abstract

The mechanical strength of commercial Al alloys rarely exceeds 700 MP. Recent studies show that nanotwinned Al alloys and other nanocolumnar metals exhibit superb mechanical behaviors but a discrepancy between tensile and hardness measurements often emerges and their orientation dependent deformation mechanisms remain unclear. Here, we inspect the mechanical response of columnar nanotwinned Al–Fe alloys with emphasis on response of grain boundaries to in-situ tension and compression tests along both in-plane and out-of-plane directions inside a scanning electron microscope. Our studies reveal ultra-high out-of-plane tensile and compressive stress, exceeding 1.8 GPa, and an in-plane tensile and compressive stress of 1.1 and 1.6 GPa, respectively. Post-mortem TEM analyses were performed to elucidate the orientation-dependent plastic anisotropy and tension-compression asymmetry in columnar nanotwinned Al–Fe alloys. This study provides an important forward step towards the understanding of deformation mechanisms in high-strength nanotwinned Al alloys and metals with nanocolumnar or non-equiaxed grains.