Abstract:
Of late, the oxide dispersion strengthening approach has gained tremendous importance in design and development of newer W alloys. As an alternative dispersoid, Y2Ti2O7 offers significant potential for excellent hardness, strength and chemical stability. Despite tremendous potential, the utility of Y2Ti2O7 in the W alloy system has not yet been documented. To bridge this gap, an attempt is made to evaluate the relative effects of Y2Ti2O7 and Y2O3 incorporation on densification, phase evolution, microstructure and mechanical properties of W-3.5Ni-1.5Fe alloys. At the outset, the pyrochlore-type Y2Ti2O7 powder was obtained by mechanical alloying of Y2O3 and TiO2 powder, followed by calcination. Subsequently, 1 wt% of Y2O3 and Y2Ti2O7 powder was incorporated individually in W-3.5Ni-1.5Fe alloys and consolidated by liquid-phase sintering. It was found that, compared to Y2O3, despite the same amount (1 wt%) of addition, Y2Ti2O7 appears as a better grain-size refiner of W. In comparison to Y2O3, the incorporation of Y2Ti2O7 results in a better combination of strength and ductility, thereby indicating enhanced toughness of the sintered W-alloy. Overall, this study substantiates that Y2Ti2O7 emerges as a suitable oxide dispersoid in W alloy systems.
