Microstructure, mechanical and thermionic emission properties of a directionally solidified LaB6-VB2 eutectic composite

Publication date: 5 November 2017
Source:Materials & Design, Volume 133
Author(s): Xinyu Yang, Pan Wang, Zhenghong Wang, Ke Hu, Hefa Cheng, Zhi Li, Jiuxing Zhang
The directionally solidified (DS) LaB6-VB2 eutectic composite is successfully prepared by the optical floating zone technique. The effect of solidification rate on the microstructure characteristic, mechanical and thermionic properties are investigated. DS LaB6-VB2 eutectic composite presents a mixed rod and lamellar microstructures as the solidification rate is increased from 8.3 to 55.6μm/s, and the formation of rod structure is ascribed to the necking of unstable lamellar. The fracture toughness in transverse section is higher than that in longitudinal section at the same rate, and the highest fracture toughness of 7.23MPa·m^1/2 in transverse section and 6.47MPa·m^1/2 in longitudinal section are obtained at V=27.8μm/s. Thermionic emission of DS LaB6-VB2 eutectic composite obeys the Longo theory, and the optimal current density of 51.92A·cm⁻² is measured at 1873K.

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