ElsevierGuiñon Pina, V.; Dalmau, A.; Amigó Borrás, V. (2015). AbstractThe tribo-electrochemical behavior of different  titanium alloys for biomedical applications sintered by powder metallurgy has been investigated. Different mechanical, electrochemical and optical techniques were used to study the influence of the chemical composition, Sn content, and the electrochemical conditions on the tribocorrosion behavior of those alloys Ti30NbxSn alloys (where "x" is the weight percentage of Sn content, 2% and 4%).Sn content increases the active and passive dissolution rate of the titanium alloys, thus increasing the mechanically activated corrosion under tribocorrosion conditions. It also increases the mechanical wear of the alloy. Prevailing electrochemical conditions between -1 and 2 V influences the wear accelerated corrosion by increasing it with the applied potential and slightly increases the mechanical wear of Ti30Nb4Sn.Wear accelerated corrosion can be predicted by existing models as a function of electrochemical and mechanical parameters of the titanium alloys.

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The electrochemical behaviour of three different near-β titanium alloys (composed by Ti, Nb and Sn) obtained by powder metallurgy for biomedical applications has been investigated. Different electrochemical and microscopy techniques were used to study the influence of the chemical composition (Sn content) and the applied potential on the microstructure and the corrosion mechanisms of those titanium alloys. Addition of Sn below 4% wt. to the titanium powder improves the microstructural homogeneity and generates an alloy with high corrosion resistance with low elastic modulus, being more suitable as a biomaterial. When the Sn content is above 4%, the corrosion resistance considerably decreases by increasing the passive dissolution rate; this effect is enhanced with the applied potential.

Titanium is an increasingly used material on industry. Based on Ti and titanium alloys characteristics, one of the most favorable processing methods is the powder metallurgy. Attending to microstructure, alloys showing β phase have singular characteristics of low elastic modulus, good specific properties and high corrosion resistance, which make β-Ti alloys very appropriated for specific uses covering a width list of fields including aeronautics or biomaterials. At this work, it has been obtained and characterized different β-Ti alloys. The processing technique has been optimized by means of an initial blender elemental followed by basic powder metallurgy. Microstructural and mechanical characterization of the studied alloys has been achieved. Results show that these kinds of alloys can be produced by this technique and the obtained properties are really interesting for a wide variety of applications.

ResumenEn la actualidad, cada vez, son más importantes en la industria las aleaciones de titanio. En especial las aleaciones tipo-β, que destacan por tener buenas propiedades resistentes y bajos módulos elásticos, en comparación con el Ti c.p. o el Ti-6Al-4V. Dentro de estas aleaciones cabe destacar las Ti-Nb con altos contenidos en elementos aleantes. En este trabajo se han obtenido, mediante pulvimetalurgia convencional, una serie de aleaciones Ti-Nb, en el rango del 20-40 % de niobio. Se ha obtenido la evolución de las propiedades de dichas aleaciones en función del porcentaje de niobio, mediante la utilización del ensayo de flexión biaxial con tres apoyos (three ball test). Palabras clavePulvimetalurgia;Ti-Nb; Flexión biaxial; Fractura; Modulo elástico; Aleaciones β-Ti. Mechanical characterization of Ti-Nb alloys by ball on three balls test AbstractNowadays titanium and titanium alloys are increasingly being used in the industry. Particularly β-Ti alloys that stand out for having great strength properties and low elastic modulus compared to Ti c.p. or Ti-6Al-4V. Among Ti alloys, Ti-Nb alloys with high contents of alloying elements are widely used. In this work Ti-Nb alloys have been obtained using conventional powder metallurgy. It has been studied the evolution of properties of these alloys as a function of the percentage of niobium. It can be noted the ball on three balls test used in order to characterize the samples. KeywordsPowder metallurgy; Ti-Nb; Ball on three balls test; Young's modulus; β-Ti alloys. INTRODUCCIÓNEl titanio y sus aleaciones tienen aplicación en diversidad de campos. Uno de los usos más conocidos tiene lugar en el de la biomedicina, por su excelente biocompatibilidad, baja densidad, resistencia a la corrosión y adecuadas propiedades mecánicas [1] . También, en otros campos como en el sector automovilístico [2] o, incluso, en el área de equipamiento deportivo [3] , está siendo ampliamente utilizado, dado que es un material que destaca por su buena relación resistencia frente a peso.Las aleaciones de titanio tipo β son las más versátiles dentro de las aleaciones de titanio. Destacan por su alta resistencia específica y por la interesante combinación de resistencia, tenacidad y resistencia a la fatiga. Además, por su bajo módulo elástico y buena resistencia a la corrosión constituyen un material muy apropiado para implantes quirúrgicos [4 y 5] .Por esta razón es de especial interés el estudio de aleaciones base titanio a partir de elementos no tóxi-cos como niobio, molibdeno o tántalo, que presentan mejor biocompatibilidad, además de un módulo elástico menor que Ti-6Al-4V por ser estabilizadores de la fase β [6 y 7] . La pulvimetalurgia es una téc-nica que permite obtener formas cercanas a la pieza acabada incluso con geometrías complejas y, dada su versatilidad, es una buena alternativa a la hora de procesar este tipo de aleaciones.Dentro de la caracterización mecánica, el ensayo de flexión biaxial, ball on three balls, ofrece ventajas respecto a los ensayos uniaxiales, como la fácil ...

Titanium is a material used in biomedicine for osseous implants due to their low density and biocompatibility. Its use in this field is limited by the lack of similarity of their stiffness with the stiffness of bones. In order to reduce this difference, powder metallurgy offers ways to develop porous materials with a reduced stiffness. The main objective of this work is to develop titanium scaffolds by space-holder technique, concretely with using two different spacers: Ammonium bicarbonate and sodium chloride. It has been studied the best way for remove spacer of green compacts, which have been sintered in high vacuum. Materials obtained by using of two spacers, have been analyzed in order to value different results in porosity, microstructural and mechanical properties. The stiffness of new materials was obtained by testing of three points in bending. This research shows that the manufacturing method of porous materials for bone replacement using space holder technique with ammonium bicarbonate or sodium chloride, allows obtained samples with slightly difference in physical, microstructural and mechanical properties.