Surface functionalization of the AA2017 aluminum alloy powder for use in additive manufacturing

Abstract

Additive Manufacturing (AM) processes, including Laser Powder Bed Fusion (L-PBF), also known as Selective Laser Melting (SLM), allow the manufacture of almost totally dense parts with complex geometry, material savings, and a minimal need for further processing. However, despite the potential application, AM of aluminum alloys is difficult due to the high laser power required to melt the material because of the high reflectivity and thermal conductivity, and low powder flowability. In this sense, the surface functionalization of the aluminum alloy powder, with an increase in roughness or a modification in the surface's chemical composition and properties (for example, surface energy and reflectivity), would allow greater incorporation of energy during the AM. Consequently, the porosity would reduce, and the part's densification and the velocity of the process would increase, in addition to making it possible to obtain a microstructure with fine and equiaxed grains through the addition of particles to the aluminum alloy powder, which act as heterogeneous nucleation sites during solidification. Besides that, the aluminum alloy absorptivity is also influenced by the wavelength of the laser used during the AM, being higher at the wavelength of the Ytterbium (Yb:YAG) and Neodymium (Nd:YAG) fiber lasers (1.06 um) than at the wavelength of the CO2 laser (10.6 um). Considering this, it is available in the Institute of Materials Science, Joining and Forming (IMAT) of Graz University of Technology (TU Graz) an L-PBF machine equipped with a Ytterbium-doped fiber laser (Yb:YAG), which results in higher energy absorption by the aluminum alloy compared to the wavelength of the CO2 laser that is present in the L-PBF machine available in the Laser Materials Processing Laboratory of Department of Materials Engineering (DEMa) at Federal University of São Carlos (UFSCar). Based on this, the objective of this research internship is to study the influence of the L-PBF parameters on the microstructure and mechanical properties of the aluminum alloy produced using the L-PBF machine present in the IMAT of TU Graz. For this, AA2017 aluminum alloy powders surface-functionalized with chemical etching with acidic HCl and basic NaOH solutions, and with deposition of TiC particles on the aluminum alloy powder will be used. Additionally, in the IMAT there is an equipment of X-ray Computed Tomography (XCT) available that will allow the evaluation of the distribution and morphology of the porosity present in the parts produced by L-PBF. Moreover, during the research internship, it will be possible to evaluate the microstructure and the mechanical properties through compression tests of the aluminum alloy produced by L-PBF with surface functionalized powders. Therefore, this research internship abroad aims to the doctoral student spend a period at the IMAT of TU Graz under the supervision of Prof. Dr. Sergio de Traglia Amancio Filho, working on the L-PBF of the AA2017 alloy using the surface-functionalized powders. (AU)