Thermo-Mechanical Properties of an NiTi-Shape Memory Alloy after Dynamic Loading
V. Grigorieva, A. Danilov and A. Razov
Saint-Petersburg State University, Universitetskii pr. 28, Saint-Petersburg, 198504, Russia
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The results of the comparative study of a quasi-equilibrium NiTi alloy's thermo-mechanical response to high-rate and quasi-static straining in the temperature range of 100-300°C, which included the Af and the Md temperatures, are considered. The existence of B2 → B19' and B2 → R → B19' martensitic transformations, associated with the heterogeneous distribution of Ni4Ti3 precipitates is shown to result in shaping of martensitic and austenitic two-way shape memories, the simultaneous presence of which determines the reversing shape memory effect. The suppression of stress-induced B2 → B19' transformation at temperatures higher than the Md temperature resulted in austenitic two-way shape memory only. Distinct dependences on the temperature of the critical stresses that initiate B2 → B19' and B2 → R → B19' martensitic transformations in austenite are shown to be the reason for the participation of the irreversible mechanisms of straining at the earliest stages of tension, whatever the strain-rate applied, thus annihilating the distinctions between the quasi-static and high-rate straining processes. As a result, the thermo-mechanical properties acquired after tension become practically independent of the strain-rate.

DOI: 10.12693/APhysPolA.128.592
PACS numbers: 62.20.fg, 81.30.Kf, 81.70.Bt