Tungsten–vanadium–yttria alloys for fusion power reactors (I): Microstructural characterization. (January 2016)

• Record Type: Journal Article
• Authors: Palacios, T.; Monge, M.A.; Pastor, J.Y.
• Is Part Of: International journal of refractory metals & hard materials. Volume 54(2016:Jan.)
• Page Start: 433
• Page End: 438
• Publication Date: 2016-01
• Subjects: Nanostructure -- Grain size -- EBSD; Heat resistant alloys -- Periodicals; Refractory materials -- Periodicals; Metallography -- Periodicals; Alliages réfractaires -- Périodiques; Matériaux réfractaires -- Périodiques; Métallographie -- Périodiques; Heat resistant alloys; Metallography; Refractory materials; Periodicals; Electronic journals; 669.73
• DOI: 10.1016/j.ijrmhm.2015.07.032
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: This study and a second part dedicated to the mechanical characterization provide a better knowledge of tungsten (W)–vanadium (V) alloys reinforced with yttrium oxide (Y2 O3 ) particles, which have been scarcely investigated. Two W alloys (W-2 or 4 wt.% V-0.5 wt.% Y2 O3 ) and a pure W material processed by powder metallurgy and consolidated by hot isostatic pressing were analysed. Along this part, the microstructure of the materials at room temperature is mainly analysed with a field emission scanning electron microscope. The densification in the compacts shows an increase with the V and Y2 O3 additions. Porosity is reduced because of the formation of a W–V solid solution and V pools that fill the pores between the grains, although such effect is mainly observed in the W2V0.5Y alloy. The microstructure of pure W is composed of coarse polyhedral grains whereas a few coarse W grains, V pools and a nanostructured area, composed of fine W grains with dispersed Y, form the alloys. In contrast to previously studied W-4 wt.% V alloys, the V pools exhibit a reduction in the oxygen content, which prevents the formation of acicular oxide structures. Finally, the refinement of the microstructure induced by the addition of V and Y2 O3 was analysed by electron backscattered diffraction measurements. Pure W presents high amount of grains over 1 μm (around 60% of the volume fraction) and only 2% below 100 nm. In the new alloys meanwhile, the population of micron size grains is highly reduced to less than 10% and grains smaller than 100 nm represent the 20%. Highlights: The addition of V produces high densification An increasing V content produces an increase in the grain size refinement. Mean grain size obtained by 3D reconstruction by EBSD analysis