Citation: Mfusi, B.J.; Popoola, P.A.; Mathe, N.R. Optimisation of the Heat Treatment Profile for Powder-Bed Fusion Built AlSi10Mg by Age Hardening and Ice-Water Quenching. Metals 2024, 14, 292. https://doi.org/ 10.3390/met14030292 Academic Editors: Hany Hassanin and Pavel Krakhmalev Received: 16 October 2023 Revised: 22 February 2024 Accepted: 25 February 2024 Published: 29 February 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). metals Article Optimisation of the Heat Treatment Profile for Powder-Bed Fusion Built AlSi10Mg by Age Hardening and Ice-Water Quenching Busisiwe J. Mfusi 1,2, * , Patricia Abimbola Popoola 2 and Ntombizodwa R. Mathe 1,2 1 Photonics Centre, Council for Scientific and Industrial Research, Meiring Naudé Road, Brummeria, Pretoria 0185, South Africa; nmathe@csir.co.za 2 Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Staatsartillerie Rd, Pretoria West, Pretoria 0183, South Africa; popoolaapi@tut.ac.za * Correspondence: siwemfusi1985@gmail.com Abstract: During powder-bed fusion (PBF), the irradiated material causes undesirable thermal stresses while experiencing large temperature oscillations over a rapid period. This requires the components produced by this technique to undergo thermal treatment. The characteristics of ad- ditively manufactured materials, which are rapid heating and cooling, do not accept conventional methods, such as thermal treatment, that alleviate stress for the removal of thermal stresses. In this research, the thermal treatment of age hardening is explored, in which AlSi10Mg is subjected to lower temperatures for longer periods of time. Other samples were thermally treated at 300 ◦ C and 400 ◦ C for various hours and quenched in ice water. This is conducted to identify the acceptable temperature and conditions that will improve the properties after thermal treatment without jeopardising other properties of the material and to investigate the effects of the thermal treatment profiles on the microstructural and mechanical characteristics of the AlSi10Mg samples. Keywords: age hardening; AlSi10Mg; thermal treatment 1. Introduction Compared to conventional production methods, the powder-bed fusion method (PBF) of additive manufacturing offers various benefits, such as excellent material use proficiency, near-net shape production, decrease in production steps, and an extraordinary level of flexi- bility and complexity of parts [1,2]. PBF can also process materials with high melting points, which are relatively hard materials. However, the exceptional characteristics of PBF, such as the rapid heating and cooling process, cause some difficulties [3]. The composite thermal narratives, extreme density of the defects and extreme degree of surface abnormalities pro- duced by the occurrence of tensile residual stresses, and inadequate ductility can negatively influence the integrity of the structural components of PBF built materials. Mechanical and thermal post-treatment have been used to try to relieve these residual stresses [4]. Most thermal post-treatment investigations for additive-made materials have been based on the implementation of reputable conservative thermal treatment techniques generally applied on the cast materials of comparable compositions. However, in previous studies by Mfusi et al. [5], it was determined that the thermal treatment profile has a negative impact on the strength and hardness of additively manufactured samples. Therefore, it is crucial to create unique thermal treatment profiles that are suitable for AM samples to fully utilise the benefits of technology in the creation of components for industrial applications [6]. Due to its castability and weldability, AlSi10Mg is generally known to be an age- hardenable alloy with good mechanical characteristics due to its near-eutectic composi- tion [7]. AlSi10Mg has been extensively studied in the conventional and additive manu- facturing arenas [8]. As a result of its great castability, reduced temperature, and reduced Metals 2024, 14, 292. https://doi.org/10.3390/met14030292 https://www.mdpi.com/journal/metals