In Process Nanocrystalline Control Consolidation of the Amorphous ZrO<SUB>2</SUB>-20 mol%Al<SUB>2</SUB>O<SUB>3</SUB> Powder

Abstract

The instrumented pulse electric discharge consolidation method is used to provide a way of in process nanocrystalline control densification of the amorphous ZrO 2 -20mol%Al 2 O 3 powder as prepared by rotating-arm reaction ball milling. The cylindrical compact height (h f ) of the amorphous ZrO 2 -20mol%Al 2 O 3 powder is found to be a dominant process variable; at I mm, it leads to the densification prior to major crystallization after a high relative density of roughly 0.86 at 800 K, and significant decreases down to 1284 K in temperature necessary to obtain the full densification under 100MPa. The rapid densification for amorphous and nanocrystalline supersaturated cubic ZrO 2 -20 mol%Al 2 O 3 is fairly well expressed by an Arrhenius-type equation of Newtonian viscous flow: η p = η po exp(Q/kT) having greatly decreasing apparent activation energy Q from 300 to 72kJ mol -1 and process viscosity η p at 1200K with decreasing h f from 14.6 to 1 mm. The Berkovich indentation testing permits us to derive a relatively low level of 4.4GPa for the value of the yield stress at room temperature in the full-density nanocrystalline ZrO 2 -20 mol%Al 2 O 3 sample having the Vickers hardness number of approximately 800 DPN.