Estudo experimental do sistema Ta-Ge e da região rica em Ta do ternário Ta-Ge-B / Experimental Investigation of the Ta-Ge System and of the Ta Rich Region of Ta-Ge-B Ternary System.

AUTOR(ES)

Antonio Augusto Araujo Pinto da Silva

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

22/05/2011

RESUMO

Jet engines are important and complex engineering devices, whose efficiency and performance are directly related to the operating temperature of the combustion chamber, the higher the gas temperature in this region, the greater the overall efficiency of the process, resulting in economy of fuel and more efficiency. Ni-based superalloys are currently used in the most critical jet engine components. Their development is coming close to a temperature limit and, therefore, there is a demand for new materials to replace them. Materials with multiphase microstructures, such as MR-Si-B alloys (MR = Refractory Metal), have a good potential for substituting superalloys in these applications. Recent studies in the Ta-Si-B system shows the stability of a phase φ whose crystal structure remains unknown due to the difficulty in obtaining a sample with large volume fraction of φ. The substitution of silicon by germanium in this system may increase the stability of φ, enabling the production of a sample by which the crystal structure of this phase can be determined. The study of the Ta-Ge-B ternary system requires the knowledge of the phase relations on its limiting binaries. However, there is no Ta-Ge phase diagram available in the literature, nor enough experimental information to propose one. Therefore, the present work aims at the experimental investigation of the phase relations on the Ta-Ge system, and of the stability of phase φ on the Ta-rich region of the Ta-Ge-B ternary system. Samples were prepared by arc melting high purity materials (tantalum, germanium and boron) under Ti-gettered argon. Their microstructures, in the as cast state as well as after heat treatments were characterized by scanning electron microscopy (SEM), energy dispersive electron probe microanalysis (EDS) and X-ray diffraction (XRD). A Ta-Ge binary phase diagram is proposed based on the results of the present work. The temperature of the Ta-rich eutetic (2444°C) was measured by optical pirometry. Due to the difficulty of arc melting samples with high Germanium contents, further investigation is still necessary for this region of the phase diagram. The results for the ternary samples suggest the stability of the φ phase in the Ta-Ge-B system.

ASSUNTO(S)

diagrama de fases phase diagram sistema ta-ge sistema ta-ge-b ta-ge system ta-ge-b system

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