Vliv velikosti zrn na mechanické vlastnosti 3Y-TZP keramiky

Effect of grain size on mechanical properties of 3Y-TZP ceramics

článek v časopise - ostatní, Jost

en

The dependence of mechanical properties of 3Y-TZP ceramics on their grain sizes in the range from 0.19 um to 2.15 um has been investigated. Vickers indentation tests were used to determine hardness and fracture toughness. The hardness decreased with increasing grain size. The fracture toughness was almost constant for ceramics with the grain size up to 0.40 um and then grew with increasing grain size up to 7.8 MPam0.5 for ceramics with grain size of 1.8 um. Above this grain size a spontaneous transformation from tetragonal to monoclinic phase occurred. Ceramic samples with grain sizes of 0.30 um and 0.78 um yielded similar bending strength, 1020 and 1011 MPa, respectively. The microstructural coarsening required for achieving larger grain size resulted in a higher scatter of strength values, which was demonstrated by a lower Weibull modulus (13.0 vs. 7.54). The mechanical properties of nanocrystalline 3Y-zirconia ceramics coarsened to the grain size range from 0.085 to 0.70 um were also investigated and compared. Differences in mechanical behaviour of investigated ceramics were observed and their possible causes discussed.

Mechanické vlastnosti 3Y-TZP keramiky byly zkoumány v závislosti na velikosti zrn v rozsahu od 0,19 um do 2,15 um. Vickersovy indentační testy byly použity pro stanovení tvrdosti a lomové houževnatosti. Tvrdost klesala s rostoucí velikostí zrn. Lomová houževnatost byla téměř konstantní pro keramiky se zrny do 0,4 um a poté rostla se zvyšující se velikosti zrn až na 7,8 MPam0,5 u keramiky se zrny o velikosti 1,8 um. U větších zrn došlo ke spontánní transformaci tetragonální fáze na monoklinickou. Keramické vzorky s velikostí zrn 0,30 um a 0,78 um měli podobnou pevnost v ohybu, 1020 a 1011 MPa. Mikrostrukturní zhrubnutí, které bylo nezbytné pro dosažení větších zrn, vedlo k vyššímu rozptylu pevností, což se projevilo snížením Weibullova modulu (13,0 vs. 7,54). Pro srovnání byly také zkoumány mechanické vlastnosti nanokrystalické 3Y-ZrO2 keramiky, jejíž zrna byla zhrublá na velikost od 0,085 do 0,70 um. Byly zjištěny rozdíly v mechanických vlastnostech zkoumaných keramik. Možné příčiny těchto rozdílů byly diskutovány.

The dependence of mechanical properties of 3Y-TZP ceramics on their grain sizes in the range from 0.19 um to 2.15 um has been investigated. Vickers indentation tests were used to determine hardness and fracture toughness. The hardness decreased with increasing grain size. The fracture toughness was almost constant for ceramics with the grain size up to 0.40 um and then grew with increasing grain size up to 7.8 MPam0.5 for ceramics with grain size of 1.8 um. Above this grain size a spontaneous transformation from tetragonal to monoclinic phase occurred. Ceramic samples with grain sizes of 0.30 um and 0.78 um yielded similar bending strength, 1020 and 1011 MPa, respectively. The microstructural coarsening required for achieving larger grain size resulted in a higher scatter of strength values, which was demonstrated by a lower Weibull modulus (13.0 vs. 7.54). The mechanical properties of nanocrystalline 3Y-zirconia ceramics coarsened to the grain size range from 0.085 to 0.70 um were also investigated and compared. Differences in mechanical behaviour of investigated ceramics were observed and their possible causes discussed.

Oxid zirkoničitý, nanokeramika, transformační zpevnění, mikrostruktura, mechanické vlastnosti

Zirconia, nanoceramics, transformation toughening, microstructure, mechanical properties

2008

01.10.2008

Institute of Chemical Technology in Prague and Institute of Inorganic Chemistry ASCR

Prague

0862-5468

Ceramics-Silikáty

52

3

165–171

7