Microstructure and Thermal Shock Resistance of Zr_7/8Ti_1/8B₂-20 vol% SiC Composites Synthesized by Mechanical Alloying and Spark Plasma Sintering

Abstract

ZrB₂-based composites are promising ultra-high temperature materials, nonetheless their poor damage tolerance and low oxidation resistance hinder their practical applications. In the present work, Zr_1–xTi_xB₂-20 vol% SiC composites were prepared based on the mechanical alloying (MA) method and spark plasma sintering (SPS) technique. The results showed that solid solution of ZrTiB₄ can be obtained by taking nano-sized ZrB₂-TiB₂ powders from the MA process. The Zr_7/8Ti_1/8B₂-20 vol% SiC composites presented higher fracture toughness due to various toughening mechanisms, such as ‘crack deflection’ and ‘pull out’ induced by the finer solid solution particles and nano-sized graphite. Consequently, Zr_7/8Ti_1/8B₂-20 vol% SiC composites possessed a residual strength of 180 MPa after thermal shock test with a temperature difference of 1000°C, while the conventional ZrB₂-20 vol% SiC composites only remained at 81.4 MPa.

GRAPHICAL ABSTRACT

Keywords:

• Mechanical alloying
• Zr_7/8Ti_1/8B₂ solid solution
• Fracture toughness
• Thermal shock resistance