Insights into grain boundary segregation and solubility limit of Cr in (TiZrNbTaCr)C

Abstract

• Cr grain boundary segregation is observed in (TiZrNbTaCr 0.125 )C and (TiZrNbTaCr 0.25 )C. • The segregation level can be controlled by adjusting initial Cr content. • Solid solubility dependence of Cr in (TiZrNbTaCr)C on temperature and initial Cr content can be used to optimize Cr addition amount for tailoring microstructure. Dense (TiZrNbTaCr)C with Cr segregation along grain boundaries (GBs) has been first proposed and fabricated by pressureless sintering at 1800-2000°C, utilizing the self-synthesized carbide powders obtained by carbothermal reduction. Cr segregation along GBs is successfully realized as expected via optimizing the initial Cr content. When Cr content is more than 11.12 at.%, Cr addition is excessive and results in Cr-rich second phase formation at triple junctions. To analyze the Cr solubility dependence on temperature and initial Cr content, the Cr content in (TiZrNbTaCr)C grains is investigated by EDS. The solubility limit of Cr in (TiZrNbTaCr)C is about 3.8 at.% at 1900°C. Finally, Vickers hardness of all the samples is measured to assess the mechanical property of (TiZrNbTaCr)C ceramics. The basic understanding of the Cr solubility limit and GB segregation feature in (TiZrNbTaCr)C have been preliminarily clarified, which may pave a potential way to design and tailor microstructure and GB feature of (TiZrNbTaCr)C for the purpose of enhancing its properties in the future.