Data and metadata from additively manufactured shape memory alloys (AM SMAs) were collected and utilized to illustrate trends and anomalies of current state-of-the-art additive manufacturing (AM) processes. Input parameters, output parameters, and properties were documented from six alloy families spanning nearly two decades of research and development: NiTi, NiMn, NiCo, FeMn, CuAl, and others. Data analyses revealed several key challenges and opportunities for advancing the field, including standardization of terminology, increased reporting of significant process parameters, and inclusion of more feedstock material information. These analyses demonstrate that improvements in these areas in future work can help ensure that reported results are easier to reproduce. Still, to date, microstructures and thermomechanical properties of SMAs have shown promising results, in some cases comparable with conventionally processed materials. This review documents some of these trends and opportunities while providing suggestions toward more data-centric reporting practices in AM SMA research. Furthermore, the dataset that was curated for this review can be analyzed in future investigations using data science approaches to further SMA alloy design and AM processes.
Shape memory alloys (SMAs) have gained much attention in the fields of aerospace engineering and elastocaloric refrigeration due to their improved performance and high work output density. Unfortunately, NiTi SMAs still suffer from poor phase compatibility issues, affecting their thermomechanical stability and functional fatigue. Previous studies have shown that small additions of substitutional elements to NiTi-based SMAs can improve those areas by further improving the degree of phase compatibility between the austenite and martensite phase transformation. The primary goal of this study was to investigate the additions of Cu and Pd to a NiTi-based SMA, and to identify processing routes to produce thermomechanically stable low-hysteresis shape memory alloys (LHSMAs) for actuator applications. The results were compared regarding hysteresis width and thermomechanical stability by way of differential scanning calorimetry, scanning electron microscopy with energy dispersive spectroscopy, and compressive thermomechanical testing. Two quaternary NiTi-based SMAs containing small additions of Cu and Pd exhibited promising results regarding low-hysteresis width and excellent thermomechanical stability.
The influence of the Hf/Zr ratio on the martensitic transformation and functional behaviour was studied in Ti30(Hf,Zr)20Ni30Cu10Co10 and Ti16(Hf,Zr)34Ni16Cu17Co17 high-entropy shape memory alloys. Hf/Zr concentration ratios were equal to 1/3, 1/1, and 3/1. The study findings revealed that substituting Hf atoms with Zr atoms increased the transformation temperatures in high-entropy Ti–Hf–Zr–Ni–Cu–Co shape memory alloys. On cooling under stress of 400 MPa, the Ms temperature increased from −123 to −45 °C when Hf/Zr ratio changed from 1/1 to 1/3 in Ti16(Hf,Zr)34Ni16Cu17Co17 alloys. Overall, this improved the functional behaviour of the alloys due to a larger volume fraction of martensite forming upon loading or cooling under stress. So, a change in Hf/Zr ratio from 3/1 to 1/3 increased the maximum recoverable strain from 0 to 6
