Generally, materials processed by SLM exhibit a very fine, non-equilibrium structure . What happens in the melt pool (melt flows,…), its stability and its dimension determine to a large extent the porosity [link] and the surface micro-roughness (such as orange-peel aspect for instance) of the final product (the macro-roughness is combined with the digitalisation, or staircase, effect). In addition, experimental results  show that the high thermal gradients occurring during SLM lead to a very fine microstructure with submicron-sized cells.
The texture is mainly dependent on the local heat fluxes and to a lesser extent on the substrate crystallography. A closer look into the microstructure of aluminium alloy samples for instance  reveals the presence of a very fine cellular–dendritic solidification structures. Three different zones can be distinguished across the melt pool. Two zones show fine and coarse cellular structures respectively; they are inside the melt pool. The heat affected zone (HAZ) is defined around the melt pool in the previous layer.
To sum up...
- The distinctive process of adding material track after track and layer after layer together with the fast and directional cooling rates during selective laser melting creates a unique structure.
- The microstructure inside a scan track is dependent on the value and direction of the thermal gradients at the border of the moving melt pool and is repeated in a similar way for every scan track. The specific SLM process conditions, such as short interaction times, high temperature gradients and the highly localized melting process, lead very fine material microstructures, hence great hardness values.
- Non-equilibrium phases of commercially available pre-alloyed powders are also accessible.
- Grains (crystallographic texture) can grow along the melt pool thermal gradients enabling potential control of the grain growth direction and general mechanical properties.
- Considering the full component macrostructure, a morphological and crystallographic texture is present and driven by the scanning strategy.
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 a. V. Gusarov, I. Yadroitsev, P. Bertrand, and I. Smurov, “Model of Radiation and Heat Transfer in Laser-Powder Interaction Zone at Selective Laser Melting,” J. Heat Transfer, vol. 131, no. 7, p. 072101, 2009.
 W. Shifeng, L. Shuai, W. Qingsong, C. Yan, Z. Sheng, and S. Yusheng, “Journal of Materials Processing Technology Effect of molten pool boundaries on the mechanical properties of selective laser melting parts,” J. Mater. Process. Tech., vol. 214, no. 11, pp. 2660–2667, 2014.
 J. Gockel, J. Fox, J. Beuth, and R. Hafley, “Integrated melt pool and microstructure control for Ti – 6Al – 4V thin wall additive manufacturing,” vol. 000, no. 000, pp. 1–5, 2014.
 E. Chlebus, T. Kurzynowski, and B. Dyba, “Microstructure and mechanical behaviour of Ti ― 6Al ― 7Nb alloy produced by selective laser melting,” vol. 62, pp. 3–10, 2011.