Characterization of the thermoelastic martensitic transformation in a NiTi alloy driven by temperature variation and external stress

Abstract

In order to test the concept of the physics of dissipation during first-order phase transitions in solids, we measured the internal friction (Q Ϫ1) and the relative shear modulus () during a thermoelastic martensitic transformation in a NiTi alloy. We adopted two approaches: temperature variation and application of external stress. This investigation of internal friction was carried out with various vibration frequencies , temperature variation rates Ṫ , and strain variation rates. The index l ͑coupling factor between phase interface and oscillating stress͒ and index n ͑rate exponent for the effective phase transformation driving force͒ have been calculated from the experimental data for each case and the values of l and n are about the same in the two ͑doped͒ NiTi samples, irrespective of whether the phase transition is driven by a temperature variation or stress induced process. We compare the values of n and l for the NiTi samples with that of the other samples ͑VO 2 ceramics and FeMn alloys͒, reinforcing the previous physical interpretations of these indices. We believe the indices n and l are indeed fingerprints of first-order phase transitions in solids. ͓S0163-1829͑97͒00230-0͔

Thermopower behavior for the shape memory alloy NiTi

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Electrochemical Preparation of Fe-Mn Alloy Film in Organic Bath

“…They have been studied thoroughly in the past 30 years (1). Fe-Mn alloys, together with Fe-Mn-Si alloys, have also been investigated as shape memory alloys because of their super elasticity (SE) and shape memory effect (SME) (2)(3). Recently, considerable interest in the exchange coupling between ferromagnetic (FM) and antiferromagnetic (AFM) thin films has been revived because of its key role in giant magnetoresistive spin valves (4)(5).…”

Shape memory effect in sputtered Ti–Ni thin films

“…from the ClCs (B2, austenite) to the monoclinic phase (B19 0 ; martensite), directly or via the intermediate rhombohedrical (Rphase) [3,4]. This transition is responsible for the shape memory effect in the TiNi compound [5][6][7]. Relevant features of this called martensitic transition, e.g.…”