Additive manufacturing reflects fundamental metallurgical principles to create materials

ScienceDaily | 1/17/2019 | Staff
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Additive manufacturing (AM), also known as 3D printing, is often used to produce engineering components. By utilising lattice structures (such as that shown below) to replace solid materials, these components are much lighter that their solid counterparts, and can be engineered in such a way that they also exhibit property combinations that are inaccessible to conventional solids. These structures are known as architected materials.

These lattice structures typically have a uniform layout with nodes all conforming to a regular array with the struts between the nodes all following common planes: and herein lies the problem.

Work - Nature - Magazine - January - Lattices

The work, detailed in Nature magazine on 17 January 2019, explains how these uniform lattices replicate the structure of a metallic single crystal: the nodes in the AM lattice are equivalent to the atoms in the single crystal and the struts are equivalent to the atomic bonds. In each of these structures, the atomic planes, or nodes are all perfectly aligned.

While in some applications, such as the high temperature end of a jet engine, single crystal materials are ideal because of their ability to withstand deformation at extreme temperatures, they have limitations relating to their mechanical performance. This limitation is also observed in AM parts with a uniform lattice structure.

Structure - Compression - Force - Deformation - Lattice

When the structure is put into compression, once the force is sufficient to cause permanent deformation, the lattice shears along one or more of the planes of nodes. With nothing to inhibit this shearing, the collapse becomes catastrophic.

In polycrystalline materials -- those with many crystals -- the alignment of the atomic planes is random, so when a shear force is in a particular direction, a crack will slow down or stop when it meets a crystal where the atoms are aligned differently from the crystal in which the crack initiated....
(Excerpt) Read more at: ScienceDaily
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