Understanding improved high temperature strength of Mo-Si-B alloy at 1100–1300 °C based on ZrB2 addition

In this study the influence of ZrB₂ addition on microstructure and high temperature compressive strength (1100 °C–1300 °C) of Mo-12Si-8.5B (at. %) alloy was investigated. Results showed that the high temperature strength was closely related to the ZrB₂ addition as well as the scale of the microstructure, and the smaller grain size of Mo-12Si-8.5B alloy resulted from ZrB₂ was beneficial to the improvement of the strength at 1100 °C but greatly deteriorated the strength at 1300 °C, which even counteracted the positive effect of Zr-rich particles derived from ZrB₂ addition. Clearly, under the premise of the same grain size, the addition of 1.5 wt% ZrB₂ significantly resulted in the improved yield strength and peak stress of the Mo-12Si-8.5B alloy within the temperature range of 1100 °C–1300 °C. Specially a remarkable increase of 30 % in yield strength was observed at 1200 °C, while at 1300 °C, the yield strength rose by 15 %. The excellent mechanical properties of the Mo-Si-B alloy with ZrB₂ addition could be attributed to a synergistic effect of intragranular Zr-rich particles dispersion strengthening, intergranular Zr-rich particles pinning effect and grain boundary purification. Additionally, these Zr-rich particles also hindered the dynamic recrystallization behavior and enhanced the softening resistance of the Mo-12Si-8.5B alloy.