Premium
Phase Transformation and Densification of an Attrition‐Milled Amorphous Yttria‐Partially‐Stabilized Zirconia–20 mol% Alumina Powder
Author(s) -
Kumagai Tatsuo,
Hongo Kazuhiro,
Kimura Hiroshi
Publication year - 2004
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2004.00644.x
Subject(s) - materials science , crystallization , tetragonal crystal system , amorphous solid , yttria stabilized zirconia , grain size , microstructure , grain growth , solid solution , cubic zirconia , mineralogy , crystallography , chemical engineering , composite material , metallurgy , crystal structure , ceramic , chemistry , engineering
Phase transformations during consolidation treatments of an attrition‐milled amorphous yttria‐partially‐stabilized zirconia (Y‐PSZ: ZrO 2 –3 mol% Y 2 O 3 )–20 mol% Al 2 O 3 powder and the resulting microstructures have been investigated. A metastable cubic phase ( c ‐ZrO 2 solid solution) together with an α‐Al 2 O 3 phase is formed in the amorphous matrix by consolidation at temperatures below 1204 K. The metastable cubic phase transforms to a stable tetragonal phase ( t ‐ZrO 2 solid solution) with an increase in the consolidation temperature. Fully dense bulk samples consisting of extremely fine tetragonal grains together with a small amount of α‐Al 2 O 3 particles could be obtained by consolidation at temperatures above 1432 K. Important features concerned with the densification behavior are as follows: (1) Marked increase in the relative density occurs after cubic crystallization and subsequent cubic‐to‐tetragonal transformation. (2) All of the consolidated bulk samples show extremely fine grain structure with grain sizes of several tens of nanometers, irrespective of the consolidation temperature. (3) The regularity of the lattice fringe contrast in each tetragonal grain seems to be kept in the vicinity of grain boundaries. These results suggest that densification of the attrition‐milled amorphous powder proceeds via superplastic flow and/or diffusional creep, rather than viscous flow of the initial amorphous phase before crystallization.