Three-dimensional printing of TiAl₃/Al₂O₃ composites

Abstract

Abstract Intermetallic/ceramic composites were fabricated by reactive infiltration of an Al melt into a porous TiO 2 preform which was prepared by indirect three-dimensional printing. At 1450°C the highly negative Gibbs energy of reaction (G r =–279.950kJ/mol) is the driving force for the redox reaction 13/2 Al+3/2 TiO 2 3/2 TiAl 3 +Al 2 O 3 to take place. Wetting of molten Al on the preform surface was improved by adding a carbon-bearing binder ((C 6 H 10 O 5 ) n , dextrin) to the powder blend, which decomposed to amorphous carbon (carbon yield 25wt.% of initial dextrin weight) after being heat-treated up to 800°C in an inert atmosphere. During annealing to 1400°C, carbon partially reduced TiO 2 at least on the surface of the grains to form Ti 3 O 5 and Ti 2 O 3 , which exhibit a significantly lower wetting angle compared to TiO 2 . In a low-oxygen-containing inert atmosphere and at 1200°C, Al melt spontaneously penetrated into the printed preform via inter-agglomerate pores (mean size 8lm) and intra-agglomerate pores (mean size 1lm). A fine-grained TiAl 3 /Al 2 O 3 composite microstructure was produced with a residual porosity of 9%.