Enhanced mechanical properties in oxide-dispersion-strengthened alloys achieved via interface segregation of cation dopants

With significantly enhanced irradiation resistance, high-temperature strength, and creep resistance, oxide-dispersion-strengthened tungsten (ODS-W) alloys present tremendous potential for high-temperature applications. However, the oxide particles tend to segregate at W grain boundary and grow up (even to micron), greatly suppressing their strengthening effect. It is always a great challenge to effectively refine and disperse the oxide particles at W grain boundary. Here, we successfully developed a new type of cation-doped W-Y2O3 alloy via a wet chemical method and subsequent low-temperature sintering. It was found that proper cation doping could not only significantly refine the intergranular Y2O3 second phase particles but also dramatically improve the sinterability of W matrix. These doping effects, as a result, simultaneously enhance the strength and ductility of the W-Y2O3 alloy. It was confirmed that the segregation of cation dopants at the W/Y2O3 interface is the origin of these doping effects. Furthermore, X-ray photoemission spectra (XPS) analyses confirmed that cation dopant segregation also obviously affects the chemical bonding (i.e., W-O bond) along the W/Y2O3 interface. As a result, the rate-limiting mechanism for W grain growth is influenced remarkably, explaining well the difference of W grain size in various cation-doped W-Y2O3 alloys. For the refinement of intergranular Y2O3 particles, it can be understood well from both thermodynamic and kinetic views. Detailedly, W/Y2O3 interfacial energy and atom mobility for Y2O3 coarsening are all limited by cation dopant segregation. More importantly, this cation-doping approach can also be applicable to other ODS alloys for enhancing their comprehensive mechanical properties.