Abstract This study investigates the fabrication of Fe–Mn–Al–Ni iron-based shape memory alloys (SMAs) using laser powder bed fusion (LPBF) across a range of laser powers. The influence of energy input on material properties was assessed by evaluating the resulting volumetric energy density. Samples were produced under both as-built conditions and subjected to in situ and ex situ treatments to enhance performance. Mechanical properties were characterized through macro-indentation, Profilometry-based Indentation Plastometry (PIP), and nanoindentation techniques, while room-temperature compression testing was conducted to assess superelastic behavior. Microstructural and phase variations were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that increasing the fabrication power improved the mechanical properties of the as-built SMAs, with the optimal performance achieved at 175 W. In situ/ex situ treatments led to a significant reduction in strength but enhanced ductility by up to 39%, along with a 52% reduction in microhardness for samples fabricated at 175 W. Overall, the LPBF-produced Fe–Mn–Al–Ni SMAs exhibited good strain recovery and stability, comparable to those produced by conventional methods. This work demonstrates the potential of LPBF in developing Fe–Mn–Al–Ni SMAs with properties matching traditionally manufactured counterparts. Graphical Abstract Mechanical behavior and microstructural features of LPBF-fabricated Fe–Mn–Al–Ni SMA under the effects of in situ and ex situ treatments

Over the past few decades, the elastocaloric effect (eCE) has emerged as the most promising alternative to vapor compression-based cooling and refrigeration devices. An overview of different forms of eC devices, based on the design of the material and the system, is captured with reported data on the cooling/heating power and efficiency. Besides experimental studies, numerical research and developed models for eCE are presented. The elastocaloric performance of NiTi Shape memory alloy has been considerably improved as a result of the unprecedented control over their microstructural, compositional, and geometrical characteristics that have been made possible by recent advancements in additive manufacturing (AM). This paper provides a thorough summary of the role of AM in the customization of NiTi-based SMAs for elastocaloric applications, with a particular emphasis on critical mechanisms such as microstructural refinement, phase stabilization, and architected design. Despite these advances, minimizing defects, managing compositional shifts, and assuring long-term cyclic stability need to be further investigated. This review emphasizes the transformative potential of AM in the development of next-generation elastocaloric materials and delineates future research directions for high-performance, scalable SMA-based cooling systems. To this end, an innovative concept of functionally graded eC material realized through additive manufacturing is introduced. These functionally graded structures pave the way to harnessing higher eC efficiency. The resulting eC materials can be 3D printed with optimal functionality and shapes. The optimized shapes, with a gradient of transformation temperatures, are expected, as described, to significantly improve the performance of the resulting systems.

The high thermal gradient and solidification velocity associated with the laser powder bed fusion process spurs formation of diverse microstructures in additively manufactured materials. This study focused on the phase composition observed in the microstructure of a laser-processed metastable titanium–niobium alloy. Through transmission electron microscopy experiments, we reveal the microstructures with several metastable phase, among which is a novel orthorhombic phase found in Nb-lean regions that is fundamentally different from the expected α′′ orthorhombic phase. Second is the O′ phase and the O′ variant selection phenomenon in laser-processed metastable β-Ti alloys. Microstructural features were found to be highly sensitive to the processing history. We further examine the mechanisms behind these phase formations and discuss how these features can influence the properties of the alloy.

Abstract The tuning of Nitinol components to achieve target transformation temperatures and mechanical properties requires careful selection of shape-setting recipes. We explore the roles of melt chemistry, raw material manufacturer, material type (wire vs. tube), heat treatment modality (air furnace vs salt), heat treatment times (1–120 min), and temperatures (350–550 °C) on the resultant transformation temperature and plateau stresses of Nitinol components. Through the compilation of hundreds of recipe permutations, we constructed time–temperature-transformation (TTT) diagrams and time–temperature-stress (TTS) diagrams which provide predictive tools to assist Nitinol medical device designers.