Abstract
The use of titanium hydride as a raw material has been an attractive alternative for the production of titanium components produced by powder metallurgy, due to increased densification of Ti compacts, greater control of contamination and cost reduction of the raw materials. However, a significant amount of hydrogen that often remains on the samples could generate degradation of the mechanical properties. Therefore, understanding decomposition mechanisms is essential to promote the components’ long life. Several studies on titanium hydride (TiH2) decomposition have been developed; nevertheless, few studies focus on the effect of the alloying elements on the dehydrogenation process. In this work, the effects of the addition of different amounts of Fe (5 and 7 wt. %) and Nb (12, 25, and 40 wt. %) as alloying elements were evaluated in detail. Results suggest that α→β transformation of Ti occurs below 800 °C; β phase can be observed at lower temperature than the expected according to the phase diagram. It was found that β phase transformation could take place during the intermediate stage of dehydrogenation. A mechanism was proposed for the effect of allying elements on the dehydrogenation process.
Highlights
Titanium and its alloys have been widely employed for high-performance components, due to their unique combination of low density, excellent mechanical properties, and high corrosion resistance.Aerospace and biomedical are currently the most important fields for applications of titanium products.Ti-based components are typically manufactured by a multi-step process of vacuum arc melting, hot rolling, scale removal, vacuum annealing machining, and surface treatment; all these fabrication stages make the final product expensive [1,2,3]
X-ray diffraction (XRD) results support that dehydrogenation finished at this temperature for alloys of Ti-Nb andand
For samples heated until a determined temperature and cooled down (VAC), the dehydrogenation reactions were interrupted and some phase transformations could not be identified since they were reverted phase transformation sequence, since the high-temperature reaction was interrupted to perform the XRD measurement at room temperature (RT) and, the intermediate phases that were formed during dehydrogenation, at a specific interval of temperature, could have been reverted to another stable phase at lower temperature
Summary
Titanium and its alloys have been widely employed for high-performance components, due to their unique combination of low density, excellent mechanical properties, and high corrosion resistance.Aerospace and biomedical are currently the most important fields for applications of titanium products.Ti-based components are typically manufactured by a multi-step process of vacuum arc melting, hot rolling, scale removal, vacuum annealing machining, and surface treatment; all these fabrication stages make the final product expensive [1,2,3]. Powder metallurgy (PM) processing offers an interesting alternative for many applications since it provides near-net-shape parts [1], enhancing the flexibility of design, minimizing the machining steps, and increasing the material yield. PM techniques allow production of components from refractory metals such as molybdenum, tungsten, or niobium, which are difficult to process by casting due to their high melting point, above. PM is a very useful alternative over casting for processing of components from elements with very different melting points that exhibit limited solubility in the liquid state and different density among them [4]. PM provides high flexibility in alloying design, overcoming limitations in casting, and achieving good homogenization of the alloying elements
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