Comparative study on microstructure and homogeneity of NiTi shape memory alloy produced by copper boat induction melting and conventional vacuum arc melting

Kabiri, Yoones; Kermanpur, A.; Foroozmehr, A.

doi:10.1016/j.vacuum.2011.09.012

Cited by 23 publications

(8 citation statements)

References 11 publications

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“…The homogeneous treatment eliminates the problem of microsegregation while O 2 contents remain as it is in the VAR process. 70 The temperature range for VAR process is 825-875 C and 950-975 C. The highest strain rate is observed at 975 C. Grain refinement can be achieved by re-crystallization of melts at high temperature, but it results in very poor fatigue properties. 71 NiTi samples produced by VIM followed by annealing at 300 C and 450 C of local canned compression specimen induce nano-crystallization of NiTi samples, In VIM, TiC compound was formed in nickel matrix when the carbon reacted with the Ti and results found a decrease in martensite transformation.…”

Section: Castingmentioning

confidence: 99%

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Fabrication of NiTi alloy: A review

Sharma

Jangra

Raj

2015

Proceedings of the Institution of Mechanical Engineers, Part L:

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Nitinol (NiTi) is categorized as a smart material which is highly recognized material for medical and other engineering applications. The behaviour of NiTi can be modified by altering the composition, modifying the porosity and applying external thermal and mechanical treatment. Due to high composition sensitivity, there are several impediments in fabrication of NiTi with conventional techniques which impel the use of additive manufacturing methods. But due to very high cost of equipments, these processes have not been commercialized till now. This paper presents a review on applications, manufacturing NiTi alloy and its various production routes from conventional to rapid prototyping, porous NiTi, effect of additives on properties of the alloy and its challenges.

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Section: Castingmentioning

confidence: 99%

“…The homogeneous treatment eliminates the problem of micro-segregation while O 2 contents remain as it is in the VAR process. 70…”

Section: Production Of Nitimentioning

confidence: 99%

Fabrication of NiTi alloy: A review

Sharma

Jangra

Raj

2015

Proceedings of the Institution of Mechanical Engineers, Part L:

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“…Several studies aiming to minimize this issue have been reported. These include the use of Ti-disk cladding [62], deploying a charging sequence and creating a screen of Titanium-Carbon on the inner surface of the graphite crucible [63], and replacing the graphite crucible with a water-cooled copper mold (copper boat) [64]. Meanwhile, in the VAR method, a carbon graphite crucible is not required, thus eliminating the carbon contamination.…”

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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“…O processo de fusão por VIM é uns dos mais utilizados para a fusão de titânio, ligas de níquel, aço inoxidável, cobalto, e ligas especiais. Neste processo, o resultado das forças eletromagnéticas fornece uma excelente agitação da massa fundida garantindo uma maior homogeneidade química e microestrutural do material produzido [7,8]. Outra técnica que tem sido utilizada em escala de laboratório para a produção de LMF e até mesmo miniatuadores destes materiais é o processo Plasma Skull PushPull (PSPP) [6].…”

Section: Introductionunclassified

Caracterização Térmica De Uma Liga De Niti Reprocessada Por Fusão a Plasma E Injeção Em Moldes Metálicos

Simões¹,

Pereira²,

Otubo³

et al. 2018

ABM Proceedings

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ResumoAs Ligas com efeito de Memória de Forma (LMF) são metais funcionais que podem recuperar grandes deformações, superiores a 5%, quando submetidos a carregamento mecânico e/ou aquecidos. Este fenômeno ainda surpreende pesquisadores e engenheiros de projetos, materiais e processos. Esses metais possibilitam o desenvolvimento de atuadores termomecânicos capazes de gerar esforço mecânico com o bloqueio da recuperação de forma. Inúmeros são os processos para obtenção dessas LMF, cada um com sua particularidade e limitação específica. Nesse contexto, este trabalho avalia o efeito do reprocessamento pela técnica Plasma Skul Push-Pull (PSPP) e do tratamento térmico de solubilização nas propriedades térmicas de transformação de fase de uma LMF 55,1Ni-44,9Ti (% em peso) obtida originalmente pelo processo de fusão por indução a vácuo (VIM). Para isso, a LMF foi refundida com uma tocha de plasma e vazada sob pressão em quatro moldes metálicos distintos (aço, bronze, alumínio e cobre). As técnicas de caracterização térmica Calorimetria Diferencial de Varredura (DSC) e Resistência Elétrica em função da Temperatura (RET) foram utilizadas para avaliar o efeito desse reprocessamento e do subsequente tratamento térmico de solubilização a 850°C em diferentes tempos. Verificou-se que a injeção em molde metálico proporciona uma significativa redução nas temperaturas de transformação de fase, da ordem de 30°C em relação ao material bruto obtido por VIM. Por fim, foi possível concluir que a LMF NiTi reprocessada mantém a transformação de fase mesmo após tratamentos de solubilização a 850°C em tempos mais longos (8 h), contrariamente ao material originalmente obtido por VIM. Palavras-chave: Ligas com memória de forma; Fusão por plasma; Solidificação; Tratamento de solubilização. THERMAL CHARACTERIZATION OF A NITI ALLOY REPROCESSED BY PLASMA MELTING AND INJECTION IN METAL MOLDS AbstractShape memory alloy (SMA) are functional metals that can recover large strain, greater than 5%, when subjected to mechanical loading and/or heated. This phenomenon still surprises researchers and design engineers, materials and processes. These metals possible to develop thermo-mechanical actuator that can generate mechanical force with the blocking of shape recovery. There are numerous processes for obtaining these SMA, each with their particularity and specific limitation. In this context, this study evaluates the effects of reprocessing by the technical Plasma Skul Push-Pull (PSPP) and solubilization thermal treatment in the thermal properties of phase transformation of the SMA 55,1Ni-44,9Ti (wt%) originally obtained by vacuum induction melting process (VIM). For this, the SMA was remelted with a plasma torch under pressure and poured into four different metal molds (steel, bronze, aluminum and copper). The thermal characterization techniques of Differential Scanning Calorimetry (DSC) and electrical resistance as a function of temperature (ERT) were used to evaluate the effect of reprocessing and subsequent solubilization heat treatment at 850°C at ...

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Comparative study on microstructure and homogeneity of NiTi shape memory alloy produced by copper boat induction melting and conventional vacuum arc melting

Cited by 23 publications

References 11 publications

Fabrication of NiTi alloy: A review

Fabrication of NiTi alloy: A review

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

Caracterização Térmica De Uma Liga De Niti Reprocessada Por Fusão a Plasma E Injeção Em Moldes Metálicos

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