Examinando por Autor "Izaguirre, Ignacio"

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Development of flexible filler ribbons by melt spinning for joining W to CuCrZr material for heat sink application
(Elsevier, 2022) Izaguirre, Ignacio; Prado, Javier de; Sánchez, Maria; Salazar, D.; Ureña, Alejandro
This paper studies the use of the melt-spinning technique as an alternative filler fabrication route to obtain flexible 80Cu-20Ti ribbons, which presents flexible and adaptability properties to cover the divertor or first wall pipe in future fusion reactors. The results showed that best conditions are achieved using a 0.8 mm diameter of the nozzle and 30 m/s of the linear wheel-speed. This condition allows to change the microstructure of the fabricated ribbons giving rise to a lower Cu4Ti intermetallic phase formation enhancing the adaptability properties. Ribbon dimensions are high enough to cover the perimeter of the pipe. Best conditions were selected to use as filler material in W-CuCrZr brazed joints at 960 ◦C. The results showed the consecution of high metallic continuity interfaces. Besides, the selected brazing conditions did not cause any thermal effect in the W base material but caused a softening effect in the CuCrZr base material as a consequence of the coarsening process of the hardening precipitates.
Exploring Cu-Ge alloys as filler materials for high vacuum brazing application of W and CuCrZr
(Elsevier, 2022-12) de Prado, Javier; Sánchez, María; Izaguirre, Ignacio; Swan, David; Ureña, Alejandro
Cu-Ge system was evaluated for its application as a filler material in W-CuCrZr joints proposed as heat sink components of the future fusion power plants. The selected compositions were rich in Cu, with the aim of retaining the ductility that characterizes copper metal. Three compositions (Cu-13.5Ge, Cu-19.5Ge and Cu-33.2Ge) and two manufacturing routes (flexible and rigid tapes) were evaluated and characterized thermally, microstructurally and mechanically. The brazing temperature decreased as the Ge content increased, giving rise to less base material thermal affectation. The microstructure was dominated by several peritectic reactions that hinder the solid state diffusion control, and three main phases (Cu solid solution, ε and ζ) were detected both in the solidified filler drop and in the joint braze. In addition, the rigid filler manufacturing route seemed to produce more continuous joints due to its more homogeneous composition. The mechanical properties indicated that both lower and richer Ge compositions gave rise to joints with higher strength.
S/TEM examination and nanomechanical response of W-Eurofer joints brazed with Cu interlayers
(Elsevier, 2022-06) Izaguirre, Ignacio; Roldán, Marcelo; de Prado, Javier; Bonache, Victoria; Sánchez, María; Ureña, Alejandro
En este artículo se realiza un estudio preliminar a microescala de una unión soldada de dos materiales que conformarán los futuros reactores de fusión. El tungsteno actuará como material de revestimiento del plasma unido a una estructura hecha de algún acero ferrítico-martensítico de activación reducida (acero tipo Eurofer). El proceso de soldadura propuesto introduce cobre como material de relleno y desarrolla el proceso térmico en una atmósfera de alto vacío a 1135 ◦C durante 10 min. La microestructura resultante se caracteriza por formar una capa de difusión en contacto con el material base de tungsteno constituido por W, Fe y Cr. Además, se forma una fase rica en hierro entre la capa de difusión y la región de soldadura de Cu. Esta banda de acero presentó dos estructuras diferentes: una estructura típica de listones de martensita y otra sin ella. En el centro de la banda de acero, los listones son reemplazados por una matriz más homogénea donde el cobre precipita nucleado debido a su enriquecimiento en este elemento durante el proceso de soldadura. Cabe destacar la presencia de dislocaciones y tensiones residuales en todas las diferentes fases que aparecen asociadas al proceso de soldadura fuerte. Esta presencia de tensiones de dislocación muestra como el análisis nanomecánico incrementa los valores de módulo y dureza de la banda de acero respecto al material base Eurofer. La capa de difusión presenta los valores más elevados en la caracterización mecánica debido a su morfología y a los componentes que la constituyen.
Wettability and microstructural evolution of copper filler in W and EUROFER brazed joints
(Springer, 2024) Izaguirre, Ignacio; Prado, Javier de; Sánchez, María; Ureña, Alejandro
In terms of wettability, active systems are characterized by a reduction in interfacial energy as the time at specific conditions is increased. This article aims to investigate the evolution of wettability and microstructure, which undergoes a critical transformation at temperatures and dwell times near brazing conditions due to their significant impact on resultant mechanical properties. The objective is to enhance wettability and prevent the formation of different phases that can occur rapidly within the brazing window conditions. Up to 1105 °C, complete fusion of the filler does not occur. However, once it happens, the expansion of the copper filler in EUROFER increases up to 400%, and the contact angle reduces from 100° to 10°, indicating an active wetting behavior. On the other hand, when copper is used with tungsten, an inert behavior is observed, maintaining the contact angle around 70°. Brazed joints carried out under the most promising wetting conditions demonstrated that at 1110 °C-1 min, various phenomena began to occur. This includes solid-state diffusion of copper in the EUROFER, following the austenitic grain boundaries, and partial dissolution of Fe in the copper braze. Increasing the brazing time from 2 to 5 min achieved high interfacial adhesion properties and controlled the diffusion layer and Fe-rich band formed at the W-braze interface, resulting in the best mechanical results (295 MPa).