Change in Mechanical Properties of Oxide Ceramics by Heat Treatment under Vacuum Condition

Abstract

iAlumina　and　Y203－partially　stabilized　zirconia（PSZ） which　were　typical　oxide　ceramics　were　heat－treated in　vacuum　in　holding　time　of 3h　and　the　temperatures　between 1300℃ and 1600℃． All　test　pieces　showed mass　loss　by　the　heat－treatment．The　amount　of　mass　loss　of　the　alumina　was　more　abounding　than　that　of the　Y203－PSZ．Though　the　mass　loss　seemed　to　be　due　to　vaporization　from　the　sample　surface，vapor species　did　not　be　identified．Bending　strength　of　alumina　and　Y203－PSZ　did　not　show　the　remarkable change　by　heat treatment　up　to 1500℃，but　decreased　suddenly　at 1600℃．It　is　considered　that　one　of　the factors　of　strength　degradation　is　the　grain　growth　by　heat-treatment．In　case　of　the　alumina，Vickers hardness　showed　the　decrease　of　about 10％ up　to1500℃ and　the　decrease　of　about 30％ at　l600℃． In　case of　the　Y203－PSZ，Vickers　hardness　showed　the　decrease　of　about 10％i n　all　tested　temperature　range．The degree　of　degradation　of　measured　physical　property　of　the　Y203 PSZ　was　smaller　than　that　of　the　alumina． The　Y203－PSZ　was　more　stable　than　the　alumina　for　heat　treatment．