首页|On the stress-temperature dependences in TiNi-based shape memory alloys
On the stress-temperature dependences in TiNi-based shape memory alloys
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NSTL
Elsevier
? 2022 Elsevier B.V.In present work, we investigated the martensitic transformations during loading/unloading cycles and stress-assisted cooling/heating cycles in TiNi-based single crystals and polycrystals with different microstructures. During loading/unloading cycles the formation of oriented B19′-martensite is only possible at stress levels higher than σcr(Ms0), so at low stress levels, below σcr(Ms0), the inelastic reversible strain, εtr, is not observed. In contrast, the inelastic reversible strain can be observed during cooling/heating cycles at low stress level σapp<σcr(Ms0). This means that the minimum stress level necessary for oriented martensite formation during cooling/heating cycles is lower than during loading/unloading cycles. An accommodating composition of both the oriented martensite variants and the thermal-induced self-accommodating martensite structure forms during stress-assisted cooling/heating cycles. On the contrary, during loading/unloading cycles the oriented martensite arises via MT from austenite or via the motion of twin boundaries in already-formed self-accommodating structure. It requires higher stress level, which is determined by high value of non-chemical energy ?GnonchA?M. Different processes occurring during loading/unloading cycles and stress-assisted cooling/heating cycles at low stress levels (σapp<σcr(Ms0)) results in different dependences Msσ(σapp) and σcr(Т) which do not coincide.
NSTL
Elsevier
