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High‐temperature strength and plastic deformation behavior of niobium diboride consolidated by spark plasma sintering
Author(s) -
Demirskyi Dmytro,
Solodkyi Ievgen,
Nishimura Toshiyuki,
Sakka Yoshio,
Vasylkiv Oleg
Publication year - 2017
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15048
Subject(s) - materials science , spark plasma sintering , flexural strength , zirconium diboride , composite material , niobium , ceramic , sintering , magnesium diboride , metallurgy , superconductivity , critical current , quantum mechanics , physics
Bulk niobium diboride ceramics were consolidated by spark plasma sintering ( SPS ) at 1900°C. SPS resulted in dense specimens with a density of 98% of the theoretical density and a mean grain size of 6 μm. During the SPS consolidation, the hexagonal boron nitride (h‐ BN ) was formed from B 2 O 3 on the powder particle surface and residual adsorbed nitrogen in the raw diboride powder. The room‐temperature strength of these NbB 2 bulks was 420 MPa. The flexural strength of the NbB 2 ceramics remained unchanged up to 1600°C. At 1700°C an increase in strength to 450 MPa was observed, which was accompanied by the disappearance of the secondary h‐ BN phase. Finally, at 1800°C signs of plastic deformation were observed. Fractographic analysis revealed a number of etching pits and steplike surfaces suggestive of high‐temperature deformation. The temperature dependence of the flexural strength of NbB 2 bulks prepared by SPS was compared with data for monolithic TiB 2 , HfB 2 and ZrB 2 . Our analysis suggested that the thermal stresses accumulated during SPS consolidation may lead to additional strengthening at elevated temperatures.