A novel nano-structured zirconium alloy prospective for high temperature applications

Zirconium alloys have many advantages for structural applications in nuclear reactors, but their use has been generally restricted at temperatures below 400°C. In this study, a novel nano-structured Zr alloy was successfully fabricated by ball milling and hot-isostatic-pressing, using Zr, Sn, ZrH2 and nano-Y2O3 as raw powders. The alloy microstructure was characterized to be uniquely featured with a very fine grain structure (mean size: ∼3 μm) and a high number density of highly-coherent, ultra-fine nano-precipitates (mean size: 4.2 nm, density: ∼2.52×1023 m−3). These nano-precipitates were identified as Y2Zr2O7, with the interfacial orientation relation of 001(010)Y2Zr2O7//000121̅1̅0Zr. This new alloy achieved remarkably-improved strength and heat resistance from room temperature up to 600°C for at least 1000 h, which is superior to all the current commercial Zr alloys, especially to Zr-2 and Zr-4 alloys with a more comparable matrix composition.