Efeitos das adições de Be, Co, Sb e Zr nas transformações de fases da liga Cu74,5Al15,0Mn10,5
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Data
2019
Autores
Silva, Leandro Santos da [UNIFESP]
Orientadores
Silva, Ricardo Alexandre Galdino da [UNIFESP]
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
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Resumo
Dentre as adições de elementos de liga ao sistema Cu-Al, a adição de Mn mostrou-se
particularmente importante pela obtenção de propriedades magnéticas e pelo aumento no
campo de estabilidade da fase β(A2). Apesar disso, o aperfeiçoamento desses materiais é
necessário para aplicação utilizando as propriedades magnéticas e de recuperação de forma. O
aperfeiçoamento de ligas metálicas geralmente ocorre por mudanças no processamento e/ou na
sua composição química. Neste trabalho, as transformações de fases das ligas
Cu72,9Al15,0Mn10,5Be1,6, Cu72,9Al15,0Mn10,5Co1,6, Cu72,9Al15,0Mn10,5Sb1,6 e Cu72,9Al15,0Mn10,5Zr1,6
inicialmente recozidas foram estudadas. Os comportamentos microestruturais, térmicos e
magnéticos foram avaliados por análise térmica diferencial, calorimetria exploratória
diferencial, medidas isocrônicas de variação da microdureza com a temperatura de têmpera,
microscopia óptica, microscopia eletrônica de varredura, espectroscopia por dispersão de
energias de raios X, difratometria de raios X e medidas de magnetização em função do campo
e da temperatura. Quatro eventos endotérmicos foram registrados nas ligas estudadas. Os
eventos constatados entre 500 K e 600 K foram associados com a transição espinodal e a
transição da fase β3 ferromagnética para β3 paramagnética. Os demais eventos, identificados
entre 700 K e 800 K, foram associados às transições: α + T3 + Mn + 1 → (B2) + α + Mn e
(B2) + α + Mn → (A2) + α, respectivamente. A intensidade dos eventos entre 700 K e 800 K
foi afetada pelo quarto elemento de liga e pode estar relacionada com as propriedades atômicas
desses elementos. As variações nas propriedades atômicas influenciam a solubilidade dos
elementos adicionados nas fases envolvidas na transição e, consequentemente, na cinética de
transição de fase e nas variações entalpicas observadas. Os resultados indicam a formação de
compostos intermetálicos pela presença de Co, Sb e Zr, mas não revelam a formação de novas
fases de Be, o que indica a possibilidade desse elemento estar dissolvido na rede cristalina das
fases já existentes na liga ternária.
On considering alloying elements added in Cu-Al system, the Mn addition is important because it induces the appearance of magnetic properties and widen the β(A2) stability field. Nevertheless, these materials improvement is necessary to their application in magnetic and shape memory devices. Generally, metallic alloys improvement occurs by change in chemical composition or processing. In this work, the phase transformations of the Cu72.9Al15.0Mn10.5Be1.6, Cu72.9Al15.0Mn10.5Co1.6, Cu72.9Al15.0Mn10.5Sb1.6 and Cu72.9Al15.0Mn10.5Zr1.6 annealed alloys were studied. The microstructure, thermal and magnetic behavior were evaluated by differential thermal analysis, differential scanning calorimetry, isochronic microhardness measurements as function of quenching temperature, optical microscopy, scanning electron microscopy, X-ray energy dispersion spectroscopy, X-ray diffractometry and magnetization measurements as function of magnetic field and temperature. It was possible observe four endothermal events in studied alloys. The spinodal transition and the magnetic transformation of the β3 phase occurred between 500 K and 600 K. The α + T3 + Mn + 1 → (B2) + α + Mn and (B2) + α + Mn → (A2) + α transitions occurred between 700 K and 800 K. The fourth alloying element affected the events intensity between 700 K and 800 K. It can be associated with the atomic properties of these elements. The changes in atomic properties influence the alloying element solubility in the phases that undergo transformations. Consequently, the kinetics and enthalpy of transition are changed. The results indicated the formation of intermetallic compounds due to the addition of Co, Sb and Zr. On another hand, new phases were not found in the Cu72.9Al15.0Mn10.5Be1.6 alloy, which indicated that this element is present in solid solutions of the ternary alloy.
On considering alloying elements added in Cu-Al system, the Mn addition is important because it induces the appearance of magnetic properties and widen the β(A2) stability field. Nevertheless, these materials improvement is necessary to their application in magnetic and shape memory devices. Generally, metallic alloys improvement occurs by change in chemical composition or processing. In this work, the phase transformations of the Cu72.9Al15.0Mn10.5Be1.6, Cu72.9Al15.0Mn10.5Co1.6, Cu72.9Al15.0Mn10.5Sb1.6 and Cu72.9Al15.0Mn10.5Zr1.6 annealed alloys were studied. The microstructure, thermal and magnetic behavior were evaluated by differential thermal analysis, differential scanning calorimetry, isochronic microhardness measurements as function of quenching temperature, optical microscopy, scanning electron microscopy, X-ray energy dispersion spectroscopy, X-ray diffractometry and magnetization measurements as function of magnetic field and temperature. It was possible observe four endothermal events in studied alloys. The spinodal transition and the magnetic transformation of the β3 phase occurred between 500 K and 600 K. The α + T3 + Mn + 1 → (B2) + α + Mn and (B2) + α + Mn → (A2) + α transitions occurred between 700 K and 800 K. The fourth alloying element affected the events intensity between 700 K and 800 K. It can be associated with the atomic properties of these elements. The changes in atomic properties influence the alloying element solubility in the phases that undergo transformations. Consequently, the kinetics and enthalpy of transition are changed. The results indicated the formation of intermetallic compounds due to the addition of Co, Sb and Zr. On another hand, new phases were not found in the Cu72.9Al15.0Mn10.5Be1.6 alloy, which indicated that this element is present in solid solutions of the ternary alloy.