Microstructure and Oxidation Behavior of Mechanically Alloyed Nb-Based Multi-Phase Superalloy

In this work, Nb-based multi-phase alloys were prepared by mechanical alloying method followed by hot-press sintering process. The effects of milling methods and milling time on the grain size and microstructure of powder were investigated. Meanwhile, the influences of sintering temperature and holding time on the density of composite, and the effects of composition and microstructure on the oxidation behavior of the alloys were investigated by OM, XRD, SEM, and EDS. The results showed that, the composite powder can be prepared by mechanical alloying and effectively increased the density by vacuum hot-press sintering. The density of alloys reached 96.3% with good properties. The oxide film mainly comprising of SiO2, Al2O3 and Nb2O5 formed during isothermal oxidation at 1573K. The introduction of Ti helped to reduce the solid solubility and diffusion rate of oxygen in matrix. The molten SiO2 prevented the growth of Nb2O5 and protect the oxide film. The alloys show good oxidation resistance.