PRESSURELESS SINTERING AND HOT ISOSTATIC PRESSING OF Ti3Al-Al2O3 INTERPENETRATING COMPOSITES

Interpenetrating phase Ti3Al-Al2O3 composites have been fabricated by reaction sintering of composite powders containing Al and TiO2 discus milled for two hours using carefully controlled heat-treatment in non-oxidizing atmospheres. Pressureless sintering has been carried out in argon at temperatures between 1330°C and 1480°C and a heating rate of 5°C/min prior to hot isostatic pressing at 200MPa for two hours at 1350°C. Densification of the composites was investigated as a function of temperature before and after hot isostatic pressing. The microstructure development and mechanical properties such as Vickers hardness of near fully dense Ti3Al-Al2O3 composites fabricated by sinter-HIP of Al-TiO2 composite powder were examined. An increase in Vickers hardness was observed after hot isostatic pressing, which can be attributed to the decrease of closed porosity in the composites. Vickers hardness of 11.0±1.0GPa was achieved for the near fully dense composite produced by pressureless sintering at 1480°C, while 12.6±1.0GPa was achieved for the near fully dense composite further subjected to hot isostatic pressing.