ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2026 39 SMJ HIGHLIGHTS June 2026 COMPOSITIONAL SENSITIVITY OF MARTENSITIC TRANSFORMATION AND MAGNETIC PROPERTIES OF CoNiAlFe FERROMAGNETIC SHAPE MEMORY ALLOYS Elisa Holzmann, Christian Hinte, Gregory Gerstein, Sebastian Herbst, and Hans Jürgen Maier The effect of minor compositional variations on the martensitic transformation and the magnetic properties of CoNiAlFe alloys was investigated using x-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry, magnetic measurements, and in situ SEM observations. Samples taken from the same bulk material with the nominal composition Co35Ni35Al28Fe2 (at. -%) were analyzed, exhibiting slight process-induced differences in composition. The results show that even small deviations of less than 1 at. -% lead to significant shifts in the transformation temperatures and the Curie temperature. The following trends are identified: An increased Ni:Al ratio raises the martensite start temperature Ms, whereas a higher Co content lowers Ms, with the Ni:Al ratio showing the dominant effect within small compositional deviations. The Ms further shows a clear increase with increased valence electron concentration (e/a). Considering these trends, Ms varies significantly among the alloys ranging from -73 to 83°C. The Curie temperature Tc increases with decreasing Al content and with decreasing Ni content when Ni was substituted by Co. While Co is the most effective element for raising Tc , it simultaneously reduces Ms, requiring a careful balance since the functional window of the alloy is defined by the temperature interval between Ms and Tc . For the current samples, a variation in Tc from -31 to 109°C is observed. The results indicate the remarkable sensitivity of structural and magnetic transformation to minor compositional deviations and highlight the potential to tune Ms and Tc through targeted composition control (Fig. 2). Fig. 2 — DSC curves of the Co35Ni35Al28Fe2 alloys with minor compositional variation. SMST 2026 HIGHLIGHTS The beautiful landscape of La Jolla, California, served as the backdrop for this year’s successful Shape Memory and Superelastic Technologies Conference and Expo- sition (SMST 2026). Held on May 4-8, the event attracted 430 attendees who enjoyed 124 technical presentations. Organized by ASM International and its SMST affiliate, the conference kicked off with a Nitinol Workshop followed by an outdoor Welcome Reception under the stars. The following day, the technical program began with an in- sightful keynote from Othmane Benafan, FASM, of NASA Glenn Research Center in Cleveland. A networking night at the Birch Aquarium at Scripps offered incredible aquatic displays and the chance for attendees to reconnect with colleagues and make new contacts in the industry. For more information on future ASM events, visit asminternational.org/events. Longtime SMST members Othmane Benafan and Alan Pelton connect during the networking event in the Birch Aquarium at Scripps.
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