Graded Al2O3/Aluminide Bodies: Processing and Microstructure

The recently developed Al 2 O 3 -aluminide alloys (i-3A) technique for fabricating near net-shape components was applied to manufacture graded bodies. During the i-3A process, Al is pressure infiltrated into porous preforms consisting of Al 2 O 3 and metal oxide. The metal oxide is reduced by the liquid aluminum, and Al 2 O 3 and the respective aluminides are formed. The process is characterized by the use of low-cost raw materials (e.g. ilmenite), low processing temperatures (600-800 °C) and short processing times when die pressure (∼1 s) or squeeze casting (> 1 min) are used as infiltration methods. In the present case, Al 2 O 3 /TiO 2 graded bodies were gas-pressure infiltrated and converted into Al 2 O 3 /TiAl 3 composites with aluminide contents varying from 0 vol% to 40 vol% TiAl 3 . The green bodies were produced by dry pressing of Al 2 O 3 /TiO 2 powder mixtures. Microstructure and interfaces between different layers of the graded composites were investigated by light microscopy and SEM. Additionally, all individual layers of the graded composite were characterized separately by hardness measurements. Basic principles for microstructural design and technical applications of graded i-3A components are discussed.