Microstructure and Texture of Metal Parts Produced by Selective Laser Melting

Selective laser melting (SLM) is an additive manufacturing technique by which structural geometrical complex parts an be created directly by selectively melting consecutive layers of powder. The high energy den sity applied by a laser beam results in high and directional thermal gra dients. In combination with the additive character of the process, this results in the formation of a unique microstructure in SLM parts which c an be altered by varying the process parameters or the constitution of t he alloy. In this work, the microstructure and texture of pure Ta, Ti-6Al-4V, AlSi 10Mg and maraging steel 18Ni(300) SLM parts are characterised by microst ructural analysis (LOM, SEM and EBSD) and X-ray diffraction. The influen ce of the unique microstructure on the mechanical properties are analyse d as well. The experimental work is supported by using a pragmatic model for SLM to calculate the temperature distribution and by using a model to estimate the plastic deformation behaviour based on the measured text ure. For most alloys, the high thermal gradients result in very fine submicro n-sized cellular-dendrites growing toward the centre of the melt pool al ong the easygrowth direction (AlSi10Mg and maraging steel 18Ni(300)). Du e to the partial remelting or previously consolidated layers, most grain s solidify epitaxially and grow across the layers. For pure metals (Ta) and Ti-6Al-4V, the solidification front remains stable, resulting in lar ge elongated grains more or less along the building direction. The competition between the epitaxial solidification and the orientation of the easy-growth of the parent grain with respect to the local heat f low direction is found to be the main determining factor to determine th e morphological as well as crystallographic texture during SLM.nrpages: 294status: publishe