ABSTRACT The Ti-β alloys have become highly demanded in industry, due to their good physical and chemical characteristics. In the present work, a Ti-13Ta-3Sn (%at) alloy was synthesized using mechanical alloying (MA) between the times of 2 and 100h. The alloys were characterized by X-ray diffraction (XRD) and analyzed by the Rietveld method with the MAUD software. The microstructural changes and the evolution of the Ti-α and Ti-β phases were characterized. Identifying the presence of a new metastable fcc phase and the synthesis of an alloy with 79.80%wt of Ti-β phase, both alloys with nanometric crystallite size.

RESUMEN Las aleaciones Ti-β se han vuelto altamente demandadas en la industria, por sus buenas características físicas y químicas. En el presente trabajo, se sintetizó una aleación Ti-13Ta-3Sn (%at) por aleado mecánico con tiempos entre 2 y 100h. Las aleaciones se caracterizaron por difracción de rayos X (DRX) y los patrones se analizaron por el método Rietveld con el software MAUD. Se caracterizaron los cambios microestructurales y la evolución de las fases Ti-α y Ti-β. Se identificó la presencia una nueva fase metaestable fcc y la síntesis de una aleación con un 79,80% en peso de fase Ti-β, ambas con tamaño de cristalita nanométrico.

ABSTRACT Nickel aluminides have been extensively studied in recent decades to replace superalloys, in some components of aircraft turbines, because they have excellent corrosion resistance. Many industrial cities have the problem of air pollution, which has forced the study of the degradation of these alloys in the presence of acid rain. The aim of this work is to study the electrochemical corrosion behavior of nickel aluminides in a medium of simulated acid rain. Potentiodynamic Polarization, Linear polarization resistance curves, Rp, Nyquist data and Bode curves obtained by electrochemical impedance spectroscopy were used to study the corrosion behavior of two intermetallic compounds. The polarization curves show that both intermetallic Ni3Al and NiAl have very similar corrosion potential, showing a slightly nobler behavior the NiAl intermetallic. The intermetallic Ni3Al has an active-passive behavior where the anode branch presents a general dissolution of the alloy, indicating that it is under cathodic control. NiAl intermetallic shows an active dissolution region, followed by a passive behavior. At longer immersion times, Ni3Al intermetallic has a higher polarization resistance, which means a lower corrosion rate.

Abstract: In this study, Al-Ni alloy ribbons in hypoeutectic, euctectic and hypereutectic compositions were obtained by melt spinning. The microstructural changes of the samples, from the as-cast to rapid solidification processes at different Cu wheel tangential velocities were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The rapid solidification caused morphological transformation of the Al-Al3Ni microstructure from acicular in the as-cast condition to globular in the melt spun ribbons and the growth of the metastable Al9Ni2 intermetallic compound, which acted as reinforcing particles. Due to the increment of the Ni content and the presence of these intermetallic compounds, with size of ~5nm, distributed in the aluminum matrix, the hardness of the alloys significantly increased from the hypoeutectic (90 VHN) to the hypereutectic (205VHN) composition.

Resumen: En este estudio, cintas de la aleación Al-Ni en las composiciones hipoeutéctica, eutéctica e hipereutéctica fueron obtenidas por la técnica de "melt spinning". Los cambios microestructurales, desde la colada hasta las cintas solidificadas rápidamente a distintas velocidades de solidificación, fueron caracterizados por difracción de Rayos X, microscopía electrónica de barrido y microscopia electrónica de transmisión. La solidificación rápida causó una transformación morfológica de la microestructura Al-Al3Ni acicular en la muestras de colada a una morfología globular en la cintas solidificadas rápidamente y el crecimiento del compuesto intermetálico metaestable Al9Ni2, el cual actuó como partícula reforzadora. Debido al incremento del contenido de Ni y la presencia de estos compuestos intermetálicos, con tamaño de ~5nm, distribuidos en la matriz de aluminio, la dureza de la aleaciones aumentó significativamente de la composición hipoeutéctica (90VHN) a la hipereutéctica (205VHN).