Estudo de moagem de alta energia e sinterização de ligas Ni-Ti-Fe

• Ano de defesa: 2017
• Autor(a) principal: Silva, Luan Rafael
• Orientador(a): Ramos, Erika Coaglia Trindade
• Banca de defesa: Sousa, Lucíola Lucena De, Souza, Renato Chaves
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Alfenas
• Programa de Pós-Graduação: Programa de Pós-Graduação em Ciência e Engenharia de Materiais
• Departamento: Instituto de Ciência e Tecnologia
• País: Brasil
• Palavras-chave em Português: Transformações martensíticas.; Ligas memória de forma.; Nitinol.
• Área do conhecimento CNPq: METALURGIA DE TRANSFORMACAO::METALURGIA DE PO
• Link de acesso: https://repositorio.unifal-mg.edu.br/handle/123456789/1074

Ni-Ti alloys, also known as Nitinol, are based on the martensitic NiTi phase (monoclinic B’19 structure) exibit unique properties such as shape memory effect and super elasticity, and its martensitic transformation temperature depends on the nitinol composition and processing. Its typical value is a temperature range between -80-100 °C. The use of alloying can contribute to avoid the undesirable Ni3Ti and NiTi2 formation. According to the isothermal section at 900oC of the Ti-Ni-Fe system, it exists a wide single-phase region extended from the NiTi to FeNi. High-energy ball milling can produce nanomaterials and metastable structures. The present work reports on the microstructural characterization of the Ni50Ti48Fe2 and Ni50Ti45Fe5 alloys prepared by high-energy ball milling and subsequent sintering. The elemental powder mixtures were processed for different times (1, 3 and 5 hours) in a planetary Fritsch P-5 ball mill under argon atmosphere using hardened steel vials (225 mL) and balls (12mm diameter), rotary speed of 200 rpm, and a ball-to-powder weight ratio of 10:1. Green bodies with 10 mm diameter were compacted by axial pressing and sintered at 900oC for 16h under argon atmosphere. Information on the phase transformations in the milled powders and sintered alloys were obtained by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and thermal analyses (DSC/TG). Only the Ni and Ti peaks were noted in XRD patterns of the Ni50Ti48Fe2 and Ni50Ti45Fe5 powders milled for 5 h. In addition, the major Ni and Ti peaks were broadened and moved toward the indicating that the iron atoms were preferentially dissolved into the Ni lattice to form extended solid solutions. The microstructures of the sintered Ni50Ti48Fe2 and Ni50Ti45Fe5 alloys were mainly formed by the NiTi phase (monoclinic B’19 structure), and their martensitic transformations were close to 50oC.