TEM investigation of hot pressed ‐10 vol.%SiC–ZrB₂ composite

Abstract

Abstract

The polytypism of SiC, phase transformation of ZrB₂ and the interfaces between SiC and ZrB₂ were investigated using high resolution TEM in a hot pressed 10 vol.%SiC‐ZrB₂ composite. In most cases, no grain boundary interphases between hexagonal ZrB₂ and 6H‐SiC phases were observed with SiC being both inter‐ and intragranular. Occasionally, 6H‐SiC transformed into 3C and 15R and hexagonal ZrB₂ transformed into cubic ZrB. High resolution TEM showed no grain boundary interphases in most regions. Energy dispersive X‐ray spectroscopy and electron energy‐loss spectroscopy analyses showed the presence of oxygen throughout the sample. The phase transformation of SiC and ZrB₂, and the interphase formation between SiC and ZrB₂ grains are discussed.

Keywords:

• UHTC's
• Interphases
• Dislocations
• ZrB₂
• SiC
• Microstructure

One of the authors, DDJ thanks the Defence Science and Technology Laboratory (Dstl) for providing the financial support for this work under contract number DSTLX‐1000015413. The authors kindly acknowledge use of the FEI TITAN 80–300 STEM facility at Imperial College London for HRTEM characterisation of interfaces.