PSI - Issue 69

Carlo Alberto Biffi et al. / Procedia Structural Integrity 69 (2025) 61 – 68

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4. Conclusion In the present work the B addition of 0.8 % at in binary Ni3Ta shape memory alloys is discussed. The following points can be highlighted: • The addition of B in small percentage does not drastically change the microstructure of the alloy, as it is uniformly dispersed in the matrix. It was shown that proper annealing treatment can provoke the precipitation of the secondary phases in the matrix. • The martensitic transformation is not suppressed by the B addition in the alloy and the characteristic temperatures remain above 200ºC, making this system suitable for high temperature applications. • Thermal cycling showed that the stability of the martensitic transformation can be reached by 2-3 cycles, beyond it is very stable. Moreover, the thermal hysteresis can be maintained below 40ºC. • The ternary alloys have mechanical response during compression significantly different with respect to the binary alloy at room temperature. The addition of B in the Ni3Ta system provoke an increase of the strain recovery in martensite and higher mechanical resistance during compression, avoiding the cracking observed in the Ni3Ta sample. It can be concluded that the addition of B in Ni3Ta system does not significantly reduce the characteristic temperatures and the corresponding heats exchanged during the martensitic transformation and the mechanical response seems to be slightly improved, probably due to the grain refining effect of B, even if this effect was not observed on the microstructure. Hot workability tests should be investigated on this system, showing the effect of the B addition with respect of the behavior of the binary system. 5. Acknowledgements The authors wish to thank Eng. Paola Bassani, Eng. Sergio Arnaboldi, Mr Giordano Carcano, Mr Marco Pini and Mr Nicola Bennato for their appreciated support in the experimental phase. The work was development in the framework of “Mind in Italy” project and sponsored by Regione Lombardia. [1] J. Ma, I. Karaman, R.D. Noebe, High temperature shape memory alloys, International Materials Reviews, Vol. 55, No. 5 (2010) 257-315. [2] K. Wu, J.L. Ma, A review of high-temperature shape memory alloys, Proc. Of SMST (2000) 153-161. [3] G.S. Firstov, J. Van Humbeeck, Yu.N. Koval, Comparison of high temperature shape memory behavior for ZrCu-based, Ti-Ni-Zr and Ti-Ni Hf alloys, Scripta Materialia 50 (2004) 243-248. [4] S. Besseghini , E. Villa, A. Tuissi, Ni-Ti-Hf shape memory alloy: effect of aging and thermal cycling, Materials Science and Engineering A273–275 (1999) 390–394. [5] X.L. Meng, Y.X. Tong, K.T. Lau, W. Cai, L.M. Zhou, L.C. Zhao, Effect of Cu addition on phase transformation of Ti-Ni-Hf high-temperature shape memory alloys, Materials Letters 57 (2002) 452-456. [6] Y. Suzuki, Ya Xu, S. Morito, K. Otsuka, K. Mitose, Effects of boron addition on microstructure and mechanical properties of Ti-Td-Nit high-temperature shape memory alloys, Materials Letters 36 (1998) 85-94. [7] D. Golberg, Ya Xu, Y. Murakami, S. Morito, K. Otsuka, T. Ueki, H. Horikawa, Characteristic of Ti50Pd30Ni20 high-temperature shape memory alloy, Intermetallics 3 (1995) 35-46. [8] G.S. Firstov, J. Van Humbeeck, Yu.N. Koval, High-temperature shape memory alloys: some recent developments, Materials Science and Engineering A378 (2004) 2-10. [9] K. Chastaing, A. Denquin, R. Portier, P. Vermaut, High-temperature shape memory alloys based on the RuNb ystem, Materials Science and Engineering A 481-482 (2008) 702-706. [10] Y. Ma, S. Yang, W. Jin, X. Liu, Ni56Mn25-xCuxGa19 (x=0,1,2,4,8) high-temperature shape-memory alloys, Journal of Alloys and Compounds 471 (2009) 570-574. [11] P.J.S. Buenconsejo, H.Y. Kim, H. Hosoda, S. Miyazaki, shape memory behavior of Ti-Ta and its potential as a high-temperature shape memory ally, Acta Materialia 57 (2009) 1068-1077. 6. References