Publication: COMPARACIÓN DE MICROESTRUCTURAS DE UNA ALEACIÓN Ti-44 AT. %Pt EN CONDICIÓN AS-CAST Y TRATADA TÉRMICAMENTE FABRICADA CON MATERIAS PRIMAS DE DISTINTA PUREZA
Date
2019
Authors
SILVA FERNÁNDEZ, SOLEDAD ANDREA
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Abstract
Este trabajo se centró en el estudio del diagrama binario Ti-Pt, en particular en la aleación Ti-44 at.%Pt. Este diagrama fue estudiado en el 2004 por Biggs et al. [1] entre los rangos de composición de 30 a 60 at.%Pt y el resultado más importante fue el descubrimiento de una nueva fase que posee estequiometría Ti4Pt3 y cuyo rango de composición se encuentra entre 41,7-43,4 at.%Pt. En el año 2012, el diagrama de fases Ti-Pt fue re-estudiado por Tello y colaboradores [2, 3] el cual, reveló que en una aleación Ti-44 at.%Pt, tanto en condición as-cast como con tratamiento térmico, existe una fase con estequiometría Ti5Pt3 que no concuerda con el diagrama de fases reportado por Biggs et al. [1] y se presume podría ser estabilizada por el oxígeno. Además, en una muestra recocida a 800 °C se observó una estructura de tipo laminar que no se logra ubicar dentro del diagrama binario y se sugiere que el oxígeno también es el factor clave de tal transformación, por lo tanto, se busca determinar si el oxígeno disuelto proveniente de materias primas es un factor que influye en las microestructuras obtenidas.Se fabricaron muestras de Ti-43,4 at.%Pt y Ti-44 at.%Pt a partir de elementos de alta pureza (6N). Tres muestras de composición Ti-44 at.%Pt fueron tratadas térmicamente a temperaturas de 1260 °C, 1050 °C y 800 °C. Las muestras, tanto en condición as-cast como tratadas térmicamente, fueron analizadas utilizando calorimetría (DSC), espectroscopía de dispersión de rayos x (EDS), microscopía electrónica de barrido (SEM) y difracción de rayos x (DRX).Finalmente, los resultados obtenidos con DSC indican que para la curva de enfriamiento del experimento realizado a 10 K/min existe un pico adicional a ~998 °C y podría ser asociado a la transformación laminar fina que se observó en la aleación tratada térmicamente a 800 °C. La aparición de Ti4Pt3 en la aleación tratada a 1050 °C es el resultado de una transformación directa desde ¿-TiPt más que de una reacción peritectoide como sugirieron Biggs et al. [1]. Luego para la aleación tratada térmicamente a 800 °C se observó que la fase Ti4Pt3 se transforma en una estructura laminar fina que contiene ¿-TiPt+Ti4Pt3 muy parecida a la obtenida por Tello [2].La fase Ti5Pt3 fue una fase recurrente en todos los casos tratados térmicamente y ningún resultado se ajustó al diagrama Ti-Pt, en consecuencia la hipótesis presentada se refuta. En cuanto a si el oxígeno es el factor de la transformación laminar en la aleación tratada a 800 °C no se pudo comprobar.
This work focused on the study of the Ti-Pt phase binary diagram, in particular of the alloy Ti-44 at.%Pt. This diagram was studied in 2004 by Biggs et al. [1] in the composition range 30 to 60 at.% Pt and the most important result was the discovery of a new phase with stoichiometry Ti4Pt3 that exists in the composition range 41.7-43.4 at%Pt. In 2012, the Ti-Pt phase diagram was re-studied by Tello and colleagues [2, 3] and, revealed that an alloy Ti-44 at.%Pt, in as-cast and heat treated condition, contains a phase of stoichiometry Ti5Pt3 that does not appear in the phase diagram reported by Biggs et al.[1] and presumably could be stabilized by oxygen. Furthermore, in a sample annealed at 800 °C, was observed a laminar morphology that can not be located within the binary diagram and it is suggested that oxygen is also the key factor in this transformation, therefore, it is sought to determine whether dissolved oxygen from raw materials is a factor that influences the obtained microstructures.Samples of Ti-43.4 at.% Pt and Ti-44 at.% Pt were made from high purity elements (6N). Three samples of composition Ti-44 at.% Pt were heat treated at temperatures of 1260 °C, 1050 °C and 800 °C. The samples, in as-cast and heat treated condition, were analyzed using calorimetry (DSC), energy dispersive x-ray spectroscopy (EDS), scanning electron microscopy (SEM) and x-ray diffraction (XRD).Finally, the results obtained with DSC showed that an additional peak at ~998 °C is observed in the cooling curve of the experiment performed at 10 K/min and could be associated with thin laminar structure that was observed in the heat treated alloy at 800 °C. The appearance of Ti4Pt3 in the alloy treated at 1050 °C responds rather to a direct transformation from ¿-TiPt that to a peritectoid reaction. Then, for the alloy heat treated at 800 °C was observed that the Ti4Pt3 phase transformed into a thin laminar structure containing ¿-TiPt + Ti4Pt3 very similar to that obtained by Tello [2].The Ti5Pt3 phase was a recurrent phase in the different samples, therefore, the results do not agree with the Ti-Pt diagram, consequently the hypothesis presented is not valid. In addition, the effect of oxygen in the laminar transformation taking place at 800 °C was not confirmed.
This work focused on the study of the Ti-Pt phase binary diagram, in particular of the alloy Ti-44 at.%Pt. This diagram was studied in 2004 by Biggs et al. [1] in the composition range 30 to 60 at.% Pt and the most important result was the discovery of a new phase with stoichiometry Ti4Pt3 that exists in the composition range 41.7-43.4 at%Pt. In 2012, the Ti-Pt phase diagram was re-studied by Tello and colleagues [2, 3] and, revealed that an alloy Ti-44 at.%Pt, in as-cast and heat treated condition, contains a phase of stoichiometry Ti5Pt3 that does not appear in the phase diagram reported by Biggs et al.[1] and presumably could be stabilized by oxygen. Furthermore, in a sample annealed at 800 °C, was observed a laminar morphology that can not be located within the binary diagram and it is suggested that oxygen is also the key factor in this transformation, therefore, it is sought to determine whether dissolved oxygen from raw materials is a factor that influences the obtained microstructures.Samples of Ti-43.4 at.% Pt and Ti-44 at.% Pt were made from high purity elements (6N). Three samples of composition Ti-44 at.% Pt were heat treated at temperatures of 1260 °C, 1050 °C and 800 °C. The samples, in as-cast and heat treated condition, were analyzed using calorimetry (DSC), energy dispersive x-ray spectroscopy (EDS), scanning electron microscopy (SEM) and x-ray diffraction (XRD).Finally, the results obtained with DSC showed that an additional peak at ~998 °C is observed in the cooling curve of the experiment performed at 10 K/min and could be associated with thin laminar structure that was observed in the heat treated alloy at 800 °C. The appearance of Ti4Pt3 in the alloy treated at 1050 °C responds rather to a direct transformation from ¿-TiPt that to a peritectoid reaction. Then, for the alloy heat treated at 800 °C was observed that the Ti4Pt3 phase transformed into a thin laminar structure containing ¿-TiPt + Ti4Pt3 very similar to that obtained by Tello [2].The Ti5Pt3 phase was a recurrent phase in the different samples, therefore, the results do not agree with the Ti-Pt diagram, consequently the hypothesis presented is not valid. In addition, the effect of oxygen in the laminar transformation taking place at 800 °C was not confirmed.
Description
Catalogado desde la version PDF de la tesis.
Keywords
ALEACION TI PT , AS-CAST , MICROESTRUCTURAS