Mechanism of interface interactions between thermodynamically stable oxides and Al containing melts

Abstract

Scandia, yttria and erbia are thermodynamically stable oxides and could be used as a structural material for crucibles, in order to avoid contamination of the melt. These oxides have similar wetting behaviour in contact with aluminium containing melts, but different interaction characteristics and different interfacial products. When yttria and erbia substrates are exposed to Al containing melts, the substrate decomposes, large amounts of Y or Er are released into the melt and a thick interaction layer consisting of a new YAlO 3 or ErAlO 3 phase is formed beneath the drop. These results were not obtained in the Sc 2 O 3 /Al system where only a slight amount of Sc was dissolved in the melt and a thin interfacial layer consisting of Al 2 O 3 was formed. The differences in the mechanism and in the nature of the reaction products of the studied systems are attributed to the thermodynamic properties of the ternary Al-Me-O systems. These properties dictate the sequence of dissolution-precipitation reactions during the wetting experiment and the final equilibrium state for each system.

Microstructural Evolution of Cr-Rich ODS Steels as a Function of Heat Treatment at 475 °C

“…It is known that at lower temperatures (such as 475°C), the YAM phase becomes unstable and decomposes to a mixture of YAP and yttria [14]. Thus, the fact that YAM has disappeared during heat treatment was not a surprise.…”

“…In the literature, there are different reports regarding the stability of the phases in the Y-Al-O system and it appears that phase stability depends on the composition of the surrounding matrix. In studies of the stability of Y-Al-O phases that focused on the Y 2 O 3 -Al 2 O 3 system, it was concluded that YAG is the most stable phase [13,14]. In a study focusing on a nickel-based austenitic steel (PM6000), Schaffer et al [15] concluded that the YAH is the most stable phase.…”