DSC-investigation of ultra thin sheet of NiTi Shape Memory Alloy
Abstract
The objective of this work was to develop and investigate the 3d-transition metal NiTi shape memory alloy for its transformation temperatures. The alloy was prepared by using chips of metallic Ni and Ti in the vacuum arc melting furnace. Melting was carried out under the protective atmosphere of Argon gas. An ultra-thin sheet (0.3mm) was prepared by cold-rolling the alloy. An intensive cold rolled sheet of NiTi was inspected for structural, microstructure, elemental composition and thermal cyclic behavior using XRD, FE-SEM, EDX and DSC studies respectively. The alloy sheet sample was annealed in the temperature range of (300-900)˚C for 20 minutes. DSC scan was carried out in the temperature range between (200 ̊C→ -60 ̊C→ 200 ̊C for as rolled, annealed and for thermal cycling. In the early stage of annealing, highly diminished martensitic and austenitic peaks in the DSC-thermo gram evidenced that the alloy microstructure structure was under high stress. An optical micrograph revealed the rolled structure of the alloy sheet. DSC examinations further revealed that the cyclic and phase-transformation behaviour of the alloy was significantly influenced by heat treatment. As a result of annealing, the transformation temperatures of austenite and martensite have shifted from 37.922 ̊C to 61.344 ̊C and from 53.453 ̊C to 72.322 ̊C respectively. The hysteresis between martensite and austenite decreases by 10.978 ̊C as the annealing temperatures increase. Stable behaviour of transformation temperature is observed after annealing at 650 ̊C and above. No change in the transformation temperatures was observed during thermal cycling. This study concludes that the variation in the transformation temperatures is the result of stress relief of martensitic plates during annealing treatment. The stable behaviour of transformations temperatures during annealing as well as during thermal cycling is due to dislocation tangling and precipitation.References
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[3] Wen C, Yu X, Zeng W, Zhao S, Wang L, Wan G, Huang S, Grover H, Chen Z. Mechanical behaviors and biomedical applications of shape memory materials: A review. AIMS Materials Science. 2018;5(4):559-90.
[4] Tarng W, Chen CJ, Lee CY, Lin CM, Lin YJ. Application of virtual reality for learning the material properties of shape memory alloys. Applied Sciences. 2019 Jan; 9 (3):580.
[5] Awan IZ, Khan AQ. Fascinating Shape Memory Alloys. Journal of the Chemical Society of Pakistan. 2018 Feb 1; 40 (1).
[6] Mahesh KK, Fernandes FB, Gurau G. Stability of thermal-induced phase transformations in the severely deformed equiatomic Ni–Ti alloys. Journal of materials science. 2012 Aug; 47 (16): 6005-14.
[7] Khademzadeh S, Parvin N, Bariani PF. Production of NiTi alloy by direct metal deposition of mechanically alloyed powder mixtures. International Journal of Precision Engineering and Manufacturing. 2015 Oct;16 (11):2333-8.
[8] Stöckel D. The shape memory effect-phenomenon, alloys and applications. California. 1995; 94539:1-3.
[9] Świec P, Zubko M, Lekston Z, Stróż D. Structure and properties of NiTi shape memory alloy after cold rolling in martensitic state.
[10] Szurman I, Kursa M. Methods for Ni-Ti based alloys preparation and their comparison. In Proceedings of conference Metal 2010, 2010 (pp. 861-866).
[11] Pelton AR, Huang GH, Moine P, Sinclair R. Effects of thermal cycling on microstructure and properties in Nitinol. Materials Science and Engineering: A. 2012 Jan 15; 532:130-8.
[12] Kus K, Breczko T. DSC-investigations of the effect of annealing temperature on the phase transformation behaviour in Ni-Ti shape memory alloy. Materials Physics and Mechanics. 2010;9 (1):75-83.
[13] Shaw JA. Tips and tricks for characterizing shape memory alloy wire: part 1—differential scanning calorimetry and basic phenomena.
[14] Jiang SY, Zhao YN, Zhang YQ, Li HU, Liang YL. Effect of solution treatment and aging on microstructural evolution and mechanical behavior of NiTi shape memory alloy. Transactions of Nonferrous Metals Society of China. 2013 Dec 1; 23 (12): 36.
[15] Uchil J, Mohanchandra KP, Mahesh KK, Kumara KG. Thermal and electrical characterization of R-phase dependence on heat-treat temperature in Nitinol. Physica B: Condensed Matter. 1998 Oct 1; 253
(1-2): 83-9.
