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Strength‐Toughness Relations in Sintered and Isostatically Hot‐Pressed ZrO 2 ‐Toughened Al 2 O 3
Author(s) -
HORI SABURO,
YOSHIMURA MASAHIRO,
SŌMIYA SHIGEYUKI
Publication year - 1986
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.1151-2916.1986.tb07401.x
Subject(s) - hot isostatic pressing , materials science , fracture toughness , toughness , composite material , pressing , hot pressing , tetragonal crystal system , cubic zirconia , metallurgy , microstructure , ceramic , crystal structure , crystallography , chemistry
The fracture toughness of fine‐grained undoped ZrO 2 ‐toughened Al 2 O 3 (ZTA) was essentially unchanged by postsintering hot isostatic pressing and increased monotonically with ZrO 2 additions up to 25 wt%. The strength of ZTA with 5 to 15 wt% tetragonal ZrO 2 , which depended monotonically on the amount of ZrO 2 present before hot isostatic pressing, was increased by pressing but became almost constant between 5 and 15 wt% ZrO 2 addition. The strength appeared to be controlled by pores before pressing and by surface flaws after pressing; the size of flaws after pressing increased with ZrO 2 content. The strength of ZTA containing mostly monoclinic ZrO 2 (20 to 25 wt%) remained almost constant despite the noticeable density increase upon hot isostatic pressing because the strength was controlled by preexisting microcracks whose extent did not change on postsintering pressing. These strength‐toughness relations in sintered and isostatically hot‐pressed ZTA are explained on the basis of R ‐curve behavior. The importance of the contribution of microcracks to the toughness of ZTA is emphasized.