In situ fabrication and microstructural evolution of Al2O3-ZrO2 nanoeutectic ceramics by a novel pulse discharge plasma assisted melting method

摘要

The present work concentrated on a novel one-step pulse discharge plasma melting method for in situ fabricating Al2O3-ZrO2 binary eutectic in a short processing time. Al2O3-ZrO2 eutectic exhibited well-aligned fibrous and colonial structure with a minimum lamellar spacing of similar to 250 nm at the growth rate of similar to 176.0 mu m/s. The lamellar spacing was well consistent with the inverse-square-root dependence on the growth rate as lambda = 2.90 x nu(-1/2), and the constant of proportionality of 2.90 was close to 3.32 predicted by the JH eutectic theory. The formation mechanism of Al2O3-ZrO2 eutectic on primary faceted-alumina crystals was also proposed. The Al2O3-ZrO2 eutectic originated from the faceted Al2O3 primary crystals, which played the leading role in the coupled growth process. The interfacial fracture behavior across the coarse intercolony regions was explored, and the fracture toughness of Al2O3-ZrO2 eutectic ceramics was comparable to those achieved by traditional directional solidification.