Thesis "EFECTO DE LA ESTRUCTURA BIOMODAL Y POROSIDAD SOBRE EL MÓDULO DE ELASTICIDAD Y ESFUERZO DE FLUENCIA EN ESPUMAS DE TI-TA-Sn".
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Date
2018
Authors
AGUIRRE BARRIENTOS, TANIA ALEJANDRA
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Abstract
A lo largo de los años se han usado diversos materiales metálicos como implantesbiomédicos, entre ellos, el acero inoxidable, aleaciones Co-Cr-Mo, aleaciones de titanioy otras aleaciones más especializadas, por ejemplo, Au-Pd. De estas, las aleaciones detitanio, destacan por su alta resistencia, baja densidad, alta resistencia a la corrosión ybiocompatibilidad. Sin embargo uno de los mayores problemas que presentan estasaleaciones es la gran diferencia que existe entre el alto módulo elástico del implantemetálico y el bajo módulo elástico del hueso, causando un problema de incompatibilidadbiomecánica conocida como "apantallamiento de tensiones". En este contexto, el objetivodel presente trabajo de memoria es estudiar el efecto de la microestructura bimodal yporosidad sobre el módulo de elasticidad y esfuerzo de fluencia en espumas de aleaciónTi-13%Ta-12%Sn (%atómico) con una porosidad de 0%, 30%, 40% y 50%.Las espumas metálicas son sintetizadas por vía pulvimetalurgia, contemplando aleadomecánico y posterior sinterización (método space-holder), para después obtener sumódulo de elasticidad. Las probetas fueron caracterizadas por medio de microscopíaelectrónica de barrido, espectroscopia de energía dispersiva y difracción de rayos X.Las espumas mostraron una distribución no homogénea de los poros y una buenahomogeneización de la estructura, con alta presencia de titanio beta en ambasmicroestructuras. Los valores de los módulos de Young y esfuerzo de fluencia siguen elcomportamiento descrito por las ecuaciones de Gibson y Ashby, obteniéndose unarelación lineal inversa respecto a la porosidad, lo cual dio para las espumas con y sinmicroestructura bimodal. Al comparar los módulos, es posible apreciar que para el casode la microestructura bimodal se obtuvo valores menores respecto a las espumas sinmicroestructura bimodal. Y en el caso del esfuerzo de fluencia, las espumas conmicroestructura bimodal presentan valores significativamente mayores.Finalmente se corrobora la hipótesis planteada de que la microestructura bimodal yporosidad adecúan el módulo de elasticidad (favorece la disminución) y esfuerzo defluencia de espumas de aleaciones de Ti-13%Ta-12%Sn (%atómico) necesarias paraestar en el cuerpo humano, siendo la porosidad el efecto más influyente.
Through the years various metallic materials have been used as biomedical implants, among them, stainless steel, Co-Cr-Mo alloys, titanium alloys and other more specialized alloys, for example, Au-Pd. Among this main metallic materials for biomedical applications, titanium alloys are getting much attention because of their high strength, low density, high resistance to corrosion and biocompatibility. However, this alloys possess high elastic modulus compared with a human bone, and hence can potentially lead to premature failure of bones. This mismatch of elastic modulus causes stress shielding, leading to implant loosening and eventual failure. In this context, the objective of this work is to study the effect of the bimodal microstructure and porosity on the modulus of elasticity and the yield stress in alloy foams Ti-13%Ta-12%Sn (%atomic) with a porosity of 0%, 30%, 40% and 50%.The metallic foams were synthesized by powder metallurgy, with mechanical alloying and sintering (space-holder method), then modulus of elasticity was obtain. The specimens were characterized by scanning electron microscopy, dispersive energy spectroscopy and X-ray diffraction.The foams showed an inhomogeneous distribution of the pores and a good homogenization of the structure, with a high presence of beta titanium in both microstructures. The Young's modulus and yield stress, follow the behavior described by the Gibson and Ashby equations, obtaining an inverse linear relation respect the porosity, in both microstructure. Comparing the modules, the bimodal microstructure showed lower values than the foams without bimodal microstructure. In the case of the yield stress, the foams with bimodal microstructure have significantly higher values.Finally, the hypothesis is corroborated, the bimodal microstructure and porosity adapt the modulus of elasticity (favors the decrease) and yield stress of foams of Ti-13%Ta-12%Sn (%atomic) necessary to be in the human body, porosity being the most influential effect.
Through the years various metallic materials have been used as biomedical implants, among them, stainless steel, Co-Cr-Mo alloys, titanium alloys and other more specialized alloys, for example, Au-Pd. Among this main metallic materials for biomedical applications, titanium alloys are getting much attention because of their high strength, low density, high resistance to corrosion and biocompatibility. However, this alloys possess high elastic modulus compared with a human bone, and hence can potentially lead to premature failure of bones. This mismatch of elastic modulus causes stress shielding, leading to implant loosening and eventual failure. In this context, the objective of this work is to study the effect of the bimodal microstructure and porosity on the modulus of elasticity and the yield stress in alloy foams Ti-13%Ta-12%Sn (%atomic) with a porosity of 0%, 30%, 40% and 50%.The metallic foams were synthesized by powder metallurgy, with mechanical alloying and sintering (space-holder method), then modulus of elasticity was obtain. The specimens were characterized by scanning electron microscopy, dispersive energy spectroscopy and X-ray diffraction.The foams showed an inhomogeneous distribution of the pores and a good homogenization of the structure, with a high presence of beta titanium in both microstructures. The Young's modulus and yield stress, follow the behavior described by the Gibson and Ashby equations, obtaining an inverse linear relation respect the porosity, in both microstructure. Comparing the modules, the bimodal microstructure showed lower values than the foams without bimodal microstructure. In the case of the yield stress, the foams with bimodal microstructure have significantly higher values.Finally, the hypothesis is corroborated, the bimodal microstructure and porosity adapt the modulus of elasticity (favors the decrease) and yield stress of foams of Ti-13%Ta-12%Sn (%atomic) necessary to be in the human body, porosity being the most influential effect.
Description
Catalogado desde la version PDF de la tesis.
Keywords
ALEACIONES DE TITANIO , ESPUMA METALICA , MICROESTRUCTURA BIMODAL