Excellent high-temperature strength and ductility of the ZrC nanoparticles dispersed molybdenum

Abstract

The interface control is critical in the development of high-performance molybdenum (Mo) alloys for high-temperature applications like space reactors. In this work, nanostructured Mo-ZrC alloy with excellent mechanical properties at both room temperature and high temperatures was fabricated by nanoscale ZrC dispersion and interface control. The average grain size of Mo-ZrC alloy is only 0.67 μm owing to the homogeneous dispersion of nanoscale ZrC particles. At room temperature, the ultimate tensile strength (UTS) and total elongation (TE) of the Mo-ZrC alloy are 928 MPa and 34.4%, respectively. At 1000 °C, the UTS is still as high as 562 MPa, which is significantly higher than those reported in oxide dispersion-strengthened Mo alloys, while the TE remains a high value of 23.5%. Additionally, the recrystallization start temperature of Mo-ZrC alloy is about 1400 °C, indicating remarkable thermal stability. First-principles calculations revealed that the interstitial oxygen reduces grain boundary cohesion, while C and ZrC could increase the fracture strength of the boundaries owing to the strong Mo-C bonds. The excellent mechanical properties and thermal stability of the Mo-ZrC alloy can be attributed to a synergistic effect of nanoscale ZrC particles dispersion strengthening, fine-grain strengthening, and grain boundary purification. The strategy could be applied to design other refractory alloys with both high strength and ductility for high-temperature applications.