Reactive processing and mechanical properties of ZrO2/NiAl intermetallic matrix composite

Abstract

10 volume% ZrO2 reinforced NiAl matrix composite(ZrO2/NiAl) was prepared by reactive hot-pressing of elemental powders. Mixtures of Ni and Al powders with reinforcing particles of partially stabilized ZrO2 have been ball-milled and hot pressed at 980 degrees C under 30 MPa. The hot-pressed billets were extruded at 1200 degrees C with an extrusion ratio of 20:2 into bars with 16mm in diameter. The tensile and compressive tests of extruded ZrO2/NiAl composite was conducted at temperature ranged 25-1000 degrees C with strain rate ranged 1.7x10(-5) - 8.3x10(-4) s(-1). The NiAl matrix showed B2 type single phase mixed with uniform distribution of ZrO2 particles added as reinforcement and Al2O3 particles included as impurities from the oxide layer of Al powders. The average size of ZrO2 reinforcement and Al2O3 were measured as about 1.1 mu m and 0.7 mu m, respectively. The hot pressed billets showed 94% density and the ZrO2/NiAl composite was fully densified up to 99% after hot extrusion. The ZrO2/NiAl composite exhibited considerable strengthening effect and showed an increase of yield strength up to 270% at temperature ranged 850-950 degrees C, The effective strengthening of the ZrO2/NiAl composite indicates a possibility to overcome the poor high temperature strength of NiAl intermetallic compounds needed for structural application above 850 degrees C.