Title

Effect on Nanoindentation in La2O3-reinforced W and W–V alloys produced by hot isostatic pressing

Conference Dates

September 29-October 4, 2019

Abstract

W is a principal candidate material for fabricating plasma facing components (PFC) in a future fusion power reactor due to its high melting temperature, good thermal conductivity, thermal stress resistance, low tritium retention and high temperature strength [1]. For these applications, the structural materials should have an operating temperature window 873-1600 K and a ductile brittle transition temperature (DBTT) in the interval 573-673 K, as well as a recrystallization temperature (RT) above1600 K [2]. La2O3 dispersion or Al, K, Si doping can improve the mechanical strength and increase the tungsten RT, although the DBTT appears not to be lowered [3]. Most of these W alloys were prepared by powder metallurgy methods, in particular by ball milling and subsequent pressure less sintering or hot isostatic pressing (HIP) [3]. Recently, W and WTi alloys reinforced with Y2O3 have been sintered by HIP [4]. The use of Ti as sintering activator and the Y2O3 dispersion result in full dense materials exhibiting improved mechanical properties and oxidation resistance [5]. However, the Y2O3 particles in a W matrix appear to be unstable at temperatures above 1600 K becoming into coarse particles of complex W-Y and W-Y-Ti oxides, which could worsen the mechanical properties. This drawback may be avoided if V is used as sintering activator. The V-W system exhibits an isomorphous phase diagram with a continuous range of solid solution [6].

The aim of the present work is to produce W and W-V alloys reinforced with La2O3 particles and investigate their microstructure and thermal stability in order to obtain a structural material with favor able properties to be used for developing PFC. W and W-V alloys reinforced with La2O3 particles have been produced by MA and subsequent HIP at 1573 K and 195 MPa. The microstructure of the consolidated alloys has been characterized by scanning electron microscopy, energy dispersive spectroscopy analyses and X-ray diffraction. The mechanical properties were studied by nanoindentation measurements. The results show that practically full dense billets of W-V, W-V-La2O3 and W-La2O3 alloys can be produced. The microstructure analysis has shown that islands of V are present in W V and W V-1La2O3 alloys. In W-1La2O3 islands of La2O3 are also present. The nanohardness of the W matrix increases with the addition of V, while decreases with the addition of La2O3.

References

[1] Davis JW, Barabash VR, Makhankov A, Plöchl L, Slattery KT. Assessment of tungsten for use in the ITER plasma facing components. J Nucl Mater 1998;258–263: 308–12.

[2] Bolt H, Barabash V, Krauss W, Linke J, Neu R, Suzuki S, et al. Materials for the plasma-facing components of fusion reactors. J Nucl Mater 2004;329–333:66–73.

[3] M. Rieth, B. Dafferner, J. Nucl. Mater. 342 (2005) 20.

[4] M.A. Monge, M.A. Auger, T. Leguey, Y. Ortega, L. Bolzoni, E. Gordo, R. Pareja, J. Nucl. Mater. 386–388 (2009) 613.

[5] M.V. Aguirre, A. Martín, J.Y. Pastor, J. LLorca, M.A. Monge, R. Pareja, Metall. Mater. Trans. 40A (2009) 2283–2290.

[6] S.V. Nagender Naidu, A.M. Sriramamurthy, M. Vijayakumar, P. Rama Rao, in: J.F. Smith (Ed.), Phase Diagrams of Vanadium Alloys, Monograph Series on Alloy Phase Diagrams, ASM International, Metal Parks, Ohio, 1989, p. 313.

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