Low-temperature accelerated sintering of high-performance oxide dispersion strengthened ultrafine grained Mo alloy

As a promising route to prepare ultrafine-grained or nanocrystalline materials, powder metallurgy has long been used to produce some metal materials with desirable microstructure. However, the challenges of rapid grain growth and torpid densification during this process always frustrate the endeavor. Especially, for the oxide dispersion strengthened (ODS) alloy, although grain growth is suppressed greatly by the traditional oxide addition, the densification of metal matrix is also hindered, especially at low temperature. To overcome such limitation, exploring a kind of oxide that can be used as both grain growth inhibitor and sintering accelerator for metal matrix will be significant. In this work, it is found that accelerated sintering can be achieved in Mo-ZrO 2 system at low temperature. The kinetic simulation results indicate that although the volume diffusion has been found to be the dominant sintering mechanism for Mo-ZrO 2 system, a significant contribution from grain boundary diffusion is also identified, which is the essential mechanism behind the accelerated sintering of this system at low temperature. Besides, the grain boundary migration also can be significantly restricted by the intergranular ZrO 2 particles. After sintering at only 1480 °C in the absence of external pressure assistance and subsequent hot forging , nanocrystalline microstructure with an average grain size of 480 nm can be obtained. The ZrO 2 second-phase particles are uniformly distributed at grain interior and grain boundaries, enhancing the recrystallization temperature and microstructural stability of metal matrix, which renders the prepared Mo-ZrO 2 alloy a stable high-strength performance characteristic even under high temperatures.