PSI - Issue 69

Diego Scaccabarozzi et al. / Procedia Structural Integrity 69 (2025) 80–88

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1. Introduction Nowadays, the demand for advanced materials in aerospace and space applications has significantly increased. For instance, there is an urgent need for lightweight structures with superior mechanical properties and vibration-damping capabilities, especially in such applications. In dynamic environments, vibration control is critical to ensure structural integrity and functionality. Shape memory alloys (SMAs), such as Nitinol, are promising for vibration-damping applications, as their exceptional superelasticity grants considerable damping capacity. These properties allow Nitinol to be the ideal choice for interface dampers that reduce transmitted vibrations without adding significant weight. Additive manufacturing (AM), particularly laser powder bed fusion (LPBF), has transformed the production of Nitinol components, enabling the fabrication of complex geometries with precise control over the microstructure and relative density of the material (Sinha et al., 2023). However, challenges such as residual stresses, porosity, and microstructural inconsistencies remain significant and can negatively impact the damping properties of LPBFed parts (Yan et al., 2024). Overcoming these challenges is essential to fully exploit Nitinol’s potential in vibration-damping systems. Several studies have demonstrated that the damping properties of metallic alloys can be enhanced through LPBF design and post-processing treatments. For example, Fiocchi et al. (2020) showed that trabecular structures produced in Ti6Al4V alloys via LPBF enhanced energy dissipation without compromising mechanical strength. Similarly, Colombo et al. (2020) demonstrated that stress-relieving thermal treatments improved the damping behaviour of LPBFed AlSi10Mg alloys. These findings emphasise the role of both structural design and thermal processing in optimising damping capacity. The latter characteristic is of paramount importance for space applications and payloads (Saggin et al., 2022; Scaccabarozzi et al., 2024a, 2024b). The LPBF production of Nitinol components has been widely explored in recent years; nevertheless, this task has been shown to face considerable challenges, as careful control of the material composition, stress state and microstructure is needed for obtaining satisfactory mechanical properties (Biffi et al., 2024). Nevertheless, the possibility of joining the design freedom granted by LPBF and the superelastic / shape-memory behaviour of Nitinol-based alloys is extremely interesting in several fields, as it may allow the production of architected structures with integrated complex functionalities (Mehrpouya et al., 2024). This research investigates the influence of post-processing heat treatments on the damping properties of LPBFed Nitinol. By understanding this relationship, this study aims to add more knowledge towards optimising the treatment processes for lightweight, high-performance interface dampers. The findings offer significant potential for vibration control systems in aerospace applications, which could allow for the design of structures that minimise mass while enhancing vibration resistance. 2. Materials and methods Sample Preparation Rectangular test samples, sized 33 × 4 × 2 mm, are fabricated by LPBF, using a Renishaw AM400 system, which employs a 400 W pulsed-wave laser and a reduced build volume. The feedstock material was gas-atomised, Ni-rich Nitinol powder with a nominal composition of Ni54Ti46 (wt.%). This composition was chosen for its excellent superelasticity and suitability for additive manufacturing. The processing parameters, summarised in Table 1, were optimised to achieve a relative density exceeding 99.5%. A schematic of the principal process parameters is depicted in Figure 1.

Table 1. Printing processing settings.

Value 150 75 Meander

Setting/Parameter

Power, P

Exposure time, t exp Scanning strategy

Argon 30 50

Atmosphere

Layer thickness Hatch distance, d h