## 1 Introduction
Upon subsequent heat treatment, the SSSS would decompose to form Al\({}_{3}\)(Sc,Zr) strengthening precipitates to pin grain boundaries, hinder dislocation motion, and effectively strengthen the final component [29,30]. Ideally, all elements would remain in SSSS after fabrication; however, as seen previously in a study by [PERSON] et al. [31], DED of Scalmalloy(r) in the as-built case has shown coarse Al\({}_{3}\)(Sc,Zr) particle formation (see Figure 1). Coarse particle formation can be linked to the slower cooling rates of DED compared with SLM [32]. Scalmalloy(r) has been found to yield the desired high strengths after fabrication and subsequent direct aging at 325 \({}^{\circ}\)C for 4 h [33], as recommended by the manufacturer [34]. Many studies have explored the impact of varying times [35, 36, 37] and temperatures [36, 37] around the recommended 325 \({}^{\circ}\)C and 4 h for powder bed processing, but few to no studies have explored the impact that delaying the artificial aging treatment has on the properties of AM components. From the literature, it has been shown that conventionally processed aluminum alloys are dramatically impacted by natural aging and subsequent artificial aging, with some studies showing property improvement [38,39]. For example, [PERSON] et al. noted that natural aging for 1 week before artificial aging of an Al7075 alloy improved the strength of the material through grain boundary precipitation and minimization of the precipitate-free zone [38]. However, some sources in the literature denote that natural aging, followed by artificial aging, can have a dramatically different impact [40; 41; 42; 43]. A study by [PERSON] et al. [41] explored the impact of prolonged natural aging prior to artificial aging of thin-walled 6005 aluminum tubes and noted that increased natural aging time followed by a constant artificial aging treatment resulted in decreased strength. The authors attributed the weakening to the evolution of \(\beta^{\prime}\) precipitates [41]. As the duration of natural aging changed with constant artificial aging treatments, a decrease in the number of precipitates and an increase in the overall size of precipitates were noted [41]. [PERSON] et al. examined the impact that natural aging before artificial aging had on aluminum 7075 [42]. The authors found that natural aging, coupled with artificial aging, showed some benefit in that peak aged condition was reached at earlier artificial aging times [42]. However, the authors concluded that, despite the benefit of reaching peak aging conditions earlier, natural aging prior to artificial aging is not particularly effective for strengthening the material [42]. From the literature, the impact of natural aging is highly dependent on the composition and chosen treatments. While minimizing the time between processing steps in small laboratory cases is possible, there can be long wait periods between stages in larger-scale production cases, such as in industry. As a result, an understanding of property and microstructural evolution is critical. This study investigates the impact of natural aging/delayed artificial aging on the resulting tensile properties and microstructural evolution by considering cases of increasing natural aging time followed by artificial aging at 325 \({}^{\circ}\)C. The tensile characteristics were examined and correlated with microstructural evolution with increasing natural aging duration. Ultimately, the study details the detrimental impact of natural aging of AM fabricated Scalmalloy(r), and a recommendation is made regarding a balance between delayed artificial aging and property diminishment. Figure 1: Coarse Al\({}_{3}\)(Sc,Zr) particle formation in as-built, DED Scalmalloy®. Reprinted with permission from Ref. [31], 2024, MDPI.