Smaller is stronger: The effect of strain hardening

Using coupled micropillar compression and micro-Laue diffraction to investigate deformation mechanisms in a complex metallic alloy Al13Co4

“…6 Looking down the [100]-direction using high resolution scanning transmission electron microscopy the core of a dislocation is found to be made up of either four, six, or ten stacking faults. 7 A small length-scale study on Al 13 Co 4 micropillars, focusing on slip on individual slip systems was carried out using micropillar compression from room temperature up to 600 C. 8 Although such micropillars were found to be stronger than bulk material, the slip patterns remained similar over the test temperature range, being made up of mainly planar faults and dislocations. 8 So far, understanding deformation in orthorhombicAl 13 Co 4 has been based on microstructural observation following deformation.…”

“…7 A small length-scale study on Al 13 Co 4 micropillars, focusing on slip on individual slip systems was carried out using micropillar compression from room temperature up to 600 C. 8 Although such micropillars were found to be stronger than bulk material, the slip patterns remained similar over the test temperature range, being made up of mainly planar faults and dislocations. 8 So far, understanding deformation in orthorhombicAl 13 Co 4 has been based on microstructural observation following deformation. The use of in-situ testing strategies enables confirmation of post-mortem observations, as well as understanding the progression of deformation in these materials.…”

“…9 The use of micro Laue diffraction allows obtaining information from the entire volume of the micropillar rather than just surface characterisation and the use of a "white" x-ray beam enables probing the development of rotational and strain gradients in both polycrystal [10][11][12] and single crystals. [13][14][15][16][17] This technique has been employed to understand deformation in terms of sequential activation of several slip systems, in various pure metals like Si, 14 Au, 14 Mo, 15 Cu, 16 and W. 17 In Laue diffraction, the position and energy of the Laue spots is dependent on the orientation of the crystal and lattice parameters; however, typical studies do not measure the energy of the diffracted spots and so the technique is usually insensitive to hydrostatic strain. In plastic deformation, changes in the crystal orientation and lattice strain gradients within the illuminated volume correspond to activation of particular slip plane and continued slip on the given plane, respectively.…”

“…Streaking of the Laue spots shows that the onset of plastic flow occurs at stresses as low as 0.8 GPa, although macroscopic yield only becomes apparent at 2 GPa. The measured misorientations, obtained from peak splitting, enable the geometrically necessary dislocation density to be estimated as Al 13 Co 4 is a complex metallic alloy (CMA) with a unit cell of 102 atoms. The orthorhombic form has a unit cell with lattice parameters of a ¼ 8.158 Å , b ¼ 12.342 Å , and c ¼ 14.452 Å .…”

“…In this study, we have used in-situ micro-Laue diffraction combined with micropillar compression of focused ion beam milled Al 13 Co 4 complex metallic alloy to investigate the evolution of deformation in Al 13 Co 4 . Streaking of the Laue spots shows that the onset of plastic flow occurs at stresses as low as 0.8 GPa, although macroscopic yield only becomes apparent at 2 GPa.…”