Strength of a 3D Printed Al 7068 Alloy Under Micro-Pillar Compression

The present work investigates the mechanical properties of as-built laser powder bed fusion (L-PBF) Aluminium 7068 alloys, together with microstructural characterization. To achieve this, micro-pillar compression (in-situ) was conducted and the state of the materials under compression were correlated with respective stress–strain curves. A cast alloy of similar bulk composition was also investigated, under identical conditions, as a benchmark material. As opposed to the larger spherical grains (about 4 µm) of the cast alloy, the L-PBF alloy exhibited typical ‘melt pool’ meso-structure, combined with refined microstructure induced by rapid cooling and gave rise to sub-micron range grain sizes. The mechanical properties of the L-PBF alloy are anisotropic in nature, due to its bi-modal type meso- and micro-structure. Cross-sectional SEM investigation was carried out on deformed micro-pillars and revealed that there exist numerous slip and shear plane networks that served as load accommodation mechanism during compression.