Desenvolvimento e caracterização de liga com memória de forma magnética

• Autor(a) principal: Quirino, Julyana Maria de Medeiros
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/24480
• topic: Memória de forma magnética; Permeabilidade magnética; NiMnGa; Martensita; Composto Heusler; Policristais; Magnetic shape memory alloy; Magnetic permeability; Martensite; Heusler alloys; Polycystals; CNPQ::ENGENHARIAS::ENGENHARIA MECANICA

Shape memory alloys (SMA) are now widely studied in academia and have increasing usage in industry, as they allow efficient performance with reduced dimensions and the possibility of sensing through the material itself. A subclass of the SMAs are the alloys with magnetic shape memory, still little explored as intelligent materials in Brazil. They combine the best properties of SMAs and common magnetostrictive materials. These alloys not only have a relevant memory effect, but can also be used in totally new applications, given their complex mechanical behavior. The magnetic shape memory alloys (MSMA) can be activated not only by the presence of a thermal stimulus, but also by the presence of a magnetic field. In this research, the polycrystalline magnetic shape memory alloys Ni51,3Mn24Ga24,7 and Ni54Mn21Ga25 were manufactured and characterized, a new characterization method was also developed through the measurement of the material’s magnetic permeability when the material is exposed to a magnetic field. Differential scanning calorimetry, X-ray diffraction, X-ray spectroscopy and scanning electron microscopy analyzes were performed to thermoanalytically and crystallographically characterize the alloys. Magnetic characterizations were also performed through magnetic saturation analysis and atomic force microscopy. From the results obtained with the developed permeability device, it was possible to establish the alloy’s permeability and also to demonstrate that there was a decrease in magnetic permeability when exposing the alloys to a constant magnetic field. Additional characterizations evidenced that the Ni54Mn21Ga25 alloy exhibited larger magnetic force than the Ni51,3Mn24Ga24,7 alloy, as well as identified that there is a hysteresis in the force behavior of these alloys in relation to the distancing and approximation from a constant magnetic field source.