Study of Ti-V-Cr-Nb High-Entropy Alloy System: Microstructure, Structure, Corrosion Behavior and Hydrogen Storage Properties
Data
2023-06-01
Autores
Yao, Jie-Yi 
Orientadores
Cardoso, Kátia Regina
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
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Resumo
Neste estudo, novas ligas de alta entropia (LAEs) do sistema Ti(30–x)VCrNb(x) (x=0, 5, 10, 15 e 20 at.%) foram projetadas, sintetizadas e caracterizadas. As características estruturais e microestruturais foram investigadas por DRX, MEV e EDX. O comportamento corrosivo foi avaliado em solução de cloreto de sódio (NaCl) a 3,5% em peso, pH 5 a 25°C por polarização potenciodinâmica e espectroscopia de impedância eletroquímica (EIS). As propriedades de armazenamento de hidrogênio foram avaliadas utilizando um equipamento tipo Sieverts. As LAEs investigadas são monofásicas, formadas por uma solução sólida com estrutura CCC e morfologias dendríticas. As curvas de polarização mostraram que a liga Ti10V35Cr35Nb20 exibiu a melhor resistência à corrosão com a menor densidade de corrente de corrosão (2,24 µA/cm2) e taxa de corrosão (1,15 × 10–2 mm/ano). A interpretação de um circuito elétrico equivalente (CEE) sugeriu a formação de um filme de óxido passivo estável nas ligas, conforme indicado pelo bom comportamento capacitivo e altos valores de impedância (>104 Ω cm2) em baixas frequências e ângulos de fase próximos a −80°. A liga livre de Nb, Ti30V35Cr35, obteve a capacidade máxima de hidrogênio de 3,62% em peso (~ 1,9 H/M) e a liga contendo Nb, Ti25V35Cr35Nb5, apresentou capacidade de armazenagem de 2,91% em peso (~ 1,6 H/M) , ambas a 20 bar de H2 à temperatura ambiente. Além disso, a adição de teor de Nb de até 10 at.% resultou na manutenção da capacidade de armazenagem em maior número de ciclos. Este estudo demonstrou que um teor apropriado de Nb pode estabilizar a fase CCC e aumentar significativamente a resistência à corrosão e a capacidade de armazenamento de hidrogênio das LAEs.
In this study, novel high-entropy alloys (HEAs) of the Ti(30–x)VCrNb(x) (x=0, 5, 10, 15, and 20 at. %) system were designed, synthesized, and characterized. The structural and microstructural features were investigated by XRD, SEM, and EDS. The corrosion behavior was evaluated in a 3.5 wt.% sodium chloride (NaCl) solution with a pH of 5 at 25°C, employing potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The hydrogen storage properties were assessed using a Sieverts’ apparatus. The investigated HEAs exhibited a single-phase BCC solid solution with dendritic microstructures. The polarization curves showed that the Ti10V35Cr35Nb20 alloy exhibited the best corrosion resistance with the lowest corrosion current density (2.24 µA/cm2) and corrosion rate (1.15×10–2 mm/yr). The interpretation of an equivalent electric circuit (EEC) suggested the formation of a stable passive oxide film on the HEAs, as indicated by good capacitive behavior and high impedance values (>104 Ω cm2) at low frequencies and phase angles close to −80°. The Nb-free alloy of Ti30V35Cr35 achieved the maximum hydrogen capacity of 3.62 wt.% (~ 1.9 H/M) and the Nb-containing alloy of Ti25V35Cr35Nb5 exhibited a hydrogen capacity of 2.91 wt.% (~ 1.6 H/M), both under 20 bar of H2 and room temperature. Additionally, the inclusion of Nb content up to 10 at.% effectively improved cycle durability. This study demonstrated that an appropriate Nb content can stabilize the BCC phase and significantly enhance the corrosion resistance and hydrogen storage capacity of the HEAs.
In this study, novel high-entropy alloys (HEAs) of the Ti(30–x)VCrNb(x) (x=0, 5, 10, 15, and 20 at. %) system were designed, synthesized, and characterized. The structural and microstructural features were investigated by XRD, SEM, and EDS. The corrosion behavior was evaluated in a 3.5 wt.% sodium chloride (NaCl) solution with a pH of 5 at 25°C, employing potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The hydrogen storage properties were assessed using a Sieverts’ apparatus. The investigated HEAs exhibited a single-phase BCC solid solution with dendritic microstructures. The polarization curves showed that the Ti10V35Cr35Nb20 alloy exhibited the best corrosion resistance with the lowest corrosion current density (2.24 µA/cm2) and corrosion rate (1.15×10–2 mm/yr). The interpretation of an equivalent electric circuit (EEC) suggested the formation of a stable passive oxide film on the HEAs, as indicated by good capacitive behavior and high impedance values (>104 Ω cm2) at low frequencies and phase angles close to −80°. The Nb-free alloy of Ti30V35Cr35 achieved the maximum hydrogen capacity of 3.62 wt.% (~ 1.9 H/M) and the Nb-containing alloy of Ti25V35Cr35Nb5 exhibited a hydrogen capacity of 2.91 wt.% (~ 1.6 H/M), both under 20 bar of H2 and room temperature. Additionally, the inclusion of Nb content up to 10 at.% effectively improved cycle durability. This study demonstrated that an appropriate Nb content can stabilize the BCC phase and significantly enhance the corrosion resistance and hydrogen storage capacity of the HEAs.
Descrição
Citação
BCC alloys, V-Ti-Cr-based alloy, hydrogen storage capacity, corrosion resistance, high-entropy alloys