PSI - Issue 69

Alberto Coda et al. / Procedia Structural Integrity 69 (2025) 26–34

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periods. The heats exchanged are in general quite low, in the range of 0.5-2 J/g, in comparison with the other SMAs [3]; their values decrease after the homogenizing thermal treatments for Ni 3 Ta while the opposite trend has been detected for the ternary alloys with Co addition. This can be an advantage because a higher amount of material is involved in the MT; this effect could be associated to the additional presence of Co partially dissolved within the matrix.

Figure 7 Overview about the martensite start transformation temperatures of investigated alloys in different annealing conditions. Table 2 summarizes DSC results for all samples in as-cast and thermal treated conditions. The overall performance of the arc-melted binary and ternary ingots is in line with the recent literature on Ni 3 Ta alloys [ 21]. In comparison to Zr and Hf, the Cu and Co addition had a rather low impact on the transformation temperatures, also the hysteresis was not reduced, but the enthalpy of transformation remained high [22]. Furthermore, the impact on the mechanical properties seems to be favorable by adding Cu and Co, making the alloy softer. Though, more work needs to be done also regarding the processing methods to enable cold working of these materials.

Table 2 DSC results summary.