Rapidly solidified powders of ZrO2/20Al(2)O(3) and ZrO2/57Al(2)O(3) (cutectic) were prepared by melting fine-particle aggregates in a high enthalpy plasma flame and then rapidly quenching the molten particles in cold water or on a copper chill plate. To ensure complete melting and homogenization of all the particles prior to quenching, the water-quenching treatment was often repeated two or even three times. The resulting melt-quenched powders and splats displayed a variety of metastable structures. The ZrO2-rich composition formed an extended solid solution phase, whereas the eutectic composition formed a nano-fibrous or amorphous structure. Upon heat treatment, both compositions developed nanocomposite structures, comprising a uniform mixture of t-ZrO2 + alpha-Al2O3 phases.