Effect of build orientation on the thermal conductivity of AlSi10Mg samples fabricated by selective laser melting

In recent years, additive manufacturing techniques such as Selective Laser Melting (SLM) have gained attention as a promising way of producing complex metal components with excellent mechanical and thermal properties. SLM uses a high energy laser beam to melt metal powders layer by layer, allowing the creation of structures that are impossible to obtain using traditional manufacturing techniques. Despite the benefits of this technology, the anisotropy of SLMproduced parts can have a significant effect on th eir thermal properties and thus it is important to investigate them, in particular the thermal conductivity. This study aims to experimentally measure the thermal conductivity of AlSi10Mg aluminium alloy cylindrical samples produced by SLM with several bui ld orientations. Using a Hot Disk equipment, the transient plane source method (TPS) was adopted to measure the samples’ thermal conductivity. This method requires that a flat sensor is located between two specimen halves. During the tests, the sensor ge nerates a heat flow rate while measuring the temperature rise on the specimen’s active surfaces. To perform these measurements, an appropriate test time is needed to minimize the influence of the boundary conditions when using a finite size specimen and it is necessary to know the volumetric specific heat of the material. The TPS method can also be used with anisotropic materials, if the thermal conductivity of the tested samples is the same in all the radial direction s. Three sets of cylindrical samples were produced with different angles between the cylinder axis and the build direction (0°, 45° and 90°) to investigate the anisotropy of thermal conductivity. The samples had a diameter of 50 mm and a height of 16 mm, which were considerably larger than th e diameter of the sensor. Therefore, the solution of the thermal conductivity equation was found with the assumption that the sensor was located in an infinitely large material, and the thermal penetration generated by the instrument did not reach the oute r boundaries of the samples. Experimental measurements were carried out at room temperature using the anisotropic module of the Hot Disk TPS 3500 instrument on all printed samples, and a negligible difference was observed between the thermal conductivity measured along the build and transverse directions. This result was further confirmed by measuring the thermal conductivity using the isotropic model of the instrument, leading to the same conclusions.