Influence of Solution Treatment Temperatures on LPBF-Produced Inconel 939 Alloy on Mechanical Performance  
[PERSON]  
Faculty of Materials Science and Engineering, Warsaw University of Technology, 00-645 Warsaw, Poland;  
939 alloy. The primary objectives are to assess the impact of sub-recrystallization (below recrystallization temperature) and recrystallization temperatures during solution treatment on mechanical performance under different conditions. This study validates the hypothesis concerning carbide redistribution and mechanical performance in LPBF-produced Inconel 939 parts through comprehensive analysis, including microstructure studies and tensile tests. The results indicate that higher heat treatment temperatures lead to significant changes in carbide redistribution and mechanical performance. For instance, at room temperature, the specimen with sub-recrystallization solution treatment temperature exhibited superior mechanical properties compared to both the as-built and recrystallization-temperature solution treatment specimens. However, at elevated temperatures (700 \({}^{\circ}\)C), a reversal in mechanical anisotropy was observed, with the vertical axis demonstrating higher tensile strength compared to the horizontal axis for all material states. Furthermore, a microstructural analysis revealed distinct changes in grain structure and precipitate distribution, particularly the migration of carbides from grain boundaries to intragranular regions. These findings underscore the importance of precise control over heat treatment parameters to achieve optimal mechanical behavior. This research provides valuable insights into optimizing LPBF processes for the Inconel 939 alloy, highlighting the need for a meticulous control of the solution treatment parameters to ensure mechanical integrity. The findings contribute to a broader understanding of material-specific responses in additive manufacturing, with significant implications for aerospace applications. 17 September 20248 October  
essential to ensure consistent part quality, emphasizing the need for comprehensive process monitoring and optimization techniques [3; 4; 5]. Nickel-based superalloys have emerged as key candidates, offering exceptional mechanical properties and high-temperature resistance. Inconel 939, in particular, has attracted attention due to its impressive blend of strength, corrosion resistance, and thermal stability at elevated temperatures. Additive manufacturing methods, especially Laser Powder Bed Fusion (LPBF), coupled with innovative heat treatment approaches, offer promising avenues for maximizing Inconel 939's potential in aerospace applications. The integration of Inconel 939 into the LPBF process presents an opportunity to address LPBF challenges and unlock new possibilities in aerospace component production. To fully exploit this potential, understanding and optimizing heat treatment protocols tailored to LPBF-produced Inconel 939 components are imperative. Standard heat treatment typically involves solution treatment and aging steps aimed at homogenizing the microstructure and enhancing mechanical properties. Solution treatment dissolves \(\gamma^{\prime}\) created during the LPBF process, facilitating a supersaturated solid solution. It also removes deleterious \(\eta\) phase, which was confirmed in Inconel 939 by [PERSON] et al. (2023) [6]. Different aging parameters focus on the growth of specific phases, thus resulting in differences between research papers. The most common aging steps are within the range of \(\gamma^{\prime}\) phase growth, as it is the primary strengthening mechanism of this alloy. [PERSON] (2018) [7] reported the upper range of the solidus phase temperature at 1250 \({}^{\circ}\)C \(\pm\) 30, higher than the reported 1235 \({}^{\circ}\)C provided by [PERSON] et al. [8] and [PERSON] et al. [9]. [PERSON] et al. [10] highlighted the impact of solution treatment temperatures, particularly recrystallization temperature, on creep properties.