Microstructure and Mechanical Properties of an Advanced Niobium Based Ultrahigh Temperature Alloy

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The microstructure and mechanical properties including room temperature fracture toughness Kq, tensile strengthσb and elongationδ at 1250°C of the Nb based alloy directionally solidified in an electron beam floating zone melting (EBFZM) furnace have been evaluated. The microstructure is primarily composed of Nb solid solution (Nbss), α-(Nb)5Si3 and (Nb)3Si phases. After directional solidification with the moving rate of electron beam gun R being respectively 2.4, 4.8 and 7.2 mm/min, the primary Nbss dendrites, Nbss + (Nb)5Si3/(Nb)3Si eutectic colonies (lamellar or rod-like) and divorced Nb silicide plates align along the longitudinal axes of the specimens. When R = 2.4 mm/min, the best directional microstructure is obtained. Directional solidification has significantly improved theσb at 1250°C and Kq. The maximumσb occurs for the specimens with R = 2.4 mm/min and is about 85.0 MPa, meanwhile, the Kq is about 19.4 MPam1/2.

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Periodical:

Materials Science Forum (Volumes 539-543)

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Edited by:

T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran

Pages:

3690-3695

Citation:

X.P. Guo et al., "Microstructure and Mechanical Properties of an Advanced Niobium Based Ultrahigh Temperature Alloy", Materials Science Forum, Vols. 539-543, pp. 3690-3695, 2007

Online since:

March 2007

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$38.00

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