Characterization of structures in metallic materials produced by additive manufacturing

Technology of production of metallic part sis steadily expanded for new ways. Some of them are methods based on powder metallurgy enabling production of parts with complex shapes which are hardly (i fat all) reachable by standard ways of machinery. In this area, one of the progressive ways is additive manufacturing, i.e. consecutive layer-by-layer compaction of the powder. Besides, unique structures of the material are produced in this way due to specifics of this processing. For example, in the selective laser melting, SLM, technique, Steep temperature changes occur. In materials in which phase transformations occur (e.g. iron), reduction of the grain size and its transformation from originally columnar shape to nearly equiaxial one exists. Moreover, due to thermal shocks production of dislocations and their rearrangement occurs so that subgrains are observed inside the equiaxed grain as well as cells surrounded by dislocation walls. Such hierarchical structures then exhibit interesting mechanical properties (P. Lejček, M. Roudnická, J. Čapek, D. Dvorský, O. Molnárová et al., Mater. Charact. 154 (2019) 222). Aluminum alloys then exhibit – due to age hardening in the course of SLM process – enhanced values of the mechanical parameters (M. Fousová, D. Dvorský, P. Lejček et al., Materials, 11 (2018) 1918).

Description

Grain structure in an AlSi9Cu3 alloy in the EBSD map with the orientation triangle corresponding to the building direction (white line indicates the melt pool boundary)