EXPERIMENTAL AND NUMERICAL INVESTIGATION OF ADDITIVE MANUFACTURED STRUCTURES

Abstract

Additive Manufacturing enabled creation of the parts of intricate shape. One of the most promising applications of AM is a creation of the structured materials the mechanical properties of which are governed by their geometry rather than microstructure. Lattice structures belong to the class of structured materials, which are formed by patterning of the unit cell topology in all space directions. Lattice structures have low weight, and their mechanical properties can be tailored for a specific applications like aerospace, biomedical and automotive engineering. Lattice structures from a range of materials like Ti and Fe alloys were manufactured and tested in the literature, but the number of articles studying the performance of lattices made of Al-Si alloys remain relatively less. Despite of this, Al-Si alloys having lower density that steels might be a cheaper alternative to Ti-based alloys. Nonetheless, the usage of the AlSi10Mg based alloys for manufacturing of lattice structures remains relatively scarce. In this research we therefore study the compressive mechanical properties of lattice structures made of AlSi10Mg alloys. The objectives of this research are to investigate the relationship between mechanical properties energy absorption and its topology, study the effect of different heat treatment on their performance and develop new lattice structures with improved properties using the Finite Element Analysis. It was found that among all topologies investigated sheet-TPMS lattice structure have highest absolute and specific mechanical properties. Strut based BCCZ lattice structure have comparable mechanical properties and much lower energy absorption, due to its catastrophic failure mode. Solid-TPMS lattices have moderate mechanical properties and energy absorption. Among the heat treatments it was found that as-built lattices have the highest mechanical properties, but the lowest energy absorption, which is related to their fibrous microstructure composed of Si-network and Al-matrix. T6 heat treatment (500 °C + Water Quench + 160 °C) results in lattices with good combination of mechanical properties and energy absorption. During this heat treatment Si-phase agglomerated to the particles and the precipitation of Mg-phase occurred. Finally, the numerical simulations to model the quasi-static compression of lattice structures were developed. Using them the stress-strain curves of newly developed lattice structures with tapered struts were predicted and compared with experiments. It was shown using simulations and experiments that the tapering of the vertical struts of BCCZ lattice structure positively affects its mechanical characteristics increasing both plateau stress and energy absorption