The effects of vacuum induction melting and electron beam melting techniques on the purity of NiTi shape memory alloys

Otubo, Jorge; Rigo, Odair Doná; Neto, C. Moura; Mei, Paulo Roberto

doi:10.1016/j.msea.2006.02.171

Cited by 77 publications

(47 citation statements)

References 8 publications

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“…Uma possível explicação para esse aumento de temperaturas de transformação pode ser a precipitação da fase metaestável Ti 3 Ni 4 que provoca a diminuição no teor de Ni na matriz. É sabido que a diminuição no teor de Ni acima da composição equiatômica provoca o aumento das temperaturas de transformação [9].…”

Section: Análise Térmica (Dsc E Dma)unclassified

Avaliação das Propriedades Termomecânicas de Fios de Liga com Memória de Forma NiTi Soldados por Pulsos de Micro TIG

et al. 2015

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Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado. Soldagem & Inspeção. 2015;20(4) Evaluation of the Thermomechanical Properties of NiTi Shape Memory Alloy Wires Welded by MICRO TIG PulsesAbstract: Micro welding can be an efficient way for joining shape memory alloys (SMA) due to high accuracy and location of heat, reducing the size of the molten zone and heat affected zone (HAZ) promoting improvements in mechanical properties in these types of joints. This study aimed to determinate variations in thermomechanical properties of welded joints of NiTi SMA wires. For this, NiTi wires (ASTM F2063) with 0.9 mm diameter were divided into two groups: (a) as received wires (NiTiA) and (b) heat treated wires at 400 °C for 20 min (NiTi400). These wires were welded by TIG process, using controlled pulses (spots). The thermomechanical characterization of micro welded wires was performed using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), uniaxial tensile tests, optical microscopy (OM), scanning electron microscopy (SEM), and Vickers microhardness. The results show the efficiency of TIG welding NiTi wires of both groups, even with the reduction of the phase transformation temperatures of the joint with respect to the original base metal. The wires with welded joints showed showed maximum superelastic strain levels of about 8% with martensite induction stresses between 400 and 500 MPa. This performance of welded joints allow the realization of superelastic cycles up to 4% deformation safely. The analysis of welded wire fracture surfaces allowed verifying ductile characteristics at the rupture process.

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Section: Análise Térmica (Dsc E Dma)unclassified

Avaliação das Propriedades Termomecânicas de Fios de Liga com Memória de Forma NiTi Soldados por Pulsos de Micro TIG

et al. 2015

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“…It is important to mention that elements used for this investigation have high purity (Grade 1 Ti, 99.80 wt.% and electrolytic Ni, 99.95 wt.%). Their transformation temperatures obtained by DSC are presented in table 1 [21][22] . After that, the buttons were placed in a melt-spun equipment to produce ribbons.…”

Section: Methodsmentioning

confidence: 99%

Effect of Spun Velocities and Composition on the R‒phase and Thermomechanical Behavior in Ti‒Ni Ribbons Electrically Heated

et al. 2016

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This work deals with structural, electrical and mechanical characterization of Ti-50.13Ni and Ti-49.62Ni (at.%) shape memory alloys (SMAs) fabricated at different circumferential wheel velocities. The effect of wheel velocity, chemical composition and heat treatments are investigated. The characterization of crystallographic phases of the Ti-Ni ribbons was carried out using X-ray diffraction. Electrical resistance variations as function of temperature (∆R/R %) were analyzed using a non-commercial technique, which consists in a thermal-adjustable bath apparatus revealing the temperatures of B2→R→B19´ two stage transformation, whereby the presence of R-phase can be definitively confirmed. The Stress-Assisted Two-Way Memory Effect was measured by an own designed apparatus with an Linear Variable Differential Transformer captor and a current controlled heating, and results indicate that the as-spun condition, promotes the Stress-Assisted Two-Way Memory Effect. On the other hand, increments in Ni content tend to decrease transformation temperatures and high wheel velocities help to the R-phase formation.

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“…The oxygen contamination is minimized since the process takes place in a high vacuum. Otubo et al [68] reported that EBM produced NiTi SMA and was a viable process resulting in ingots with a carbon content as low as 70 ppm. It also showed that the martensitic transformation is decreased by the presence of carbon and oxygen and depending upon the degree of contamination, where the deviation from the reference curve can be as high as 100 °C.…”

Section: Bulk Micromachined Smamentioning

confidence: 99%

Micromachined Shape-Memory-Alloy Microactuators and Their Application in Biomedical Devices

2015

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Shape memory alloys (SMAs) are a class of smart materials characterized by shape memory effect and pseudo-elastic behavior. They have the capability to retain their original form when subjected to certain stimuli, such as heat or a magnetic field. These unique properties have attracted many researchers to seek their application in various fields including transportation, aerospace, and biomedical. The ease process adaption from semiconductor manufacturing technology provides many opportunities for designing micro-scale devices using this material. This paper gives an overview of the fabrication and manufacturing technique of thin-film and bulk micromachined SMAs. Key features such as material properties, transformation temperature, material composition, and actuation method are also presented. The application and micromechanism for both thin-film and bulk SMA are described. Finally, the microactuator devices emphasized for biomedical applications such as microgrippers and micropumps are highlighted. The presented review will provide information for researchers who are actively working on the development of SMA-based microscale biomedical devices.

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The effects of vacuum induction melting and electron beam melting techniques on the purity of NiTi shape memory alloys

Cited by 77 publications

References 8 publications

Avaliação das Propriedades Termomecânicas de Fios de Liga com Memória de Forma NiTi Soldados por Pulsos de Micro TIG

Avaliação das Propriedades Termomecânicas de Fios de Liga com Memória de Forma NiTi Soldados por Pulsos de Micro TIG

Effect of Spun Velocities and Composition on the R‒phase and Thermomechanical Behavior in Ti‒Ni Ribbons Electrically Heated

Micromachined Shape-Memory-Alloy Microactuators and Their Application in Biomedical Devices

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