Fracture toughness distribution of alumina-titanium functionally graded materials fabricated by spark plasma sintering

This paper deals with fracture behavior of alumina (Al2O3) - pure titanium (Ti) functionally graded materials (FGMs) fabricated by the spark plasma sintering (SPS) technique. The FGMs in which Ti content was decreased from Ti substrate to Al2O3 surface in a stepwise manner were fabricated using powders of Al2O3 and Ti or Al2O3 and Ti hydride (TiH2). The FGM without large flaws and delamination was fabricated when the powders of Al2O3 and Ti were used, while the FGM had many traces of drop off and flaws in its graded layer when the powders of Al2O3 and TiH2 were used. The material combination of Al2O3 and Ti powders was appropriate to fabricate the FGM consisting of Al2O3 and Ti. The Vickers hardness in the Ti substrate and Al2O3 surface in the Al2O3-Ti FGM was comparable to each material fabricated by SPS. The fracture toughness of the Al2O3-Ti FGM increased in the Ti substrate, while that of its graded layer was low. The Al2O3-Ti FGM has a potential as a material with high hardness at the surface and high fracture toughness at the substrate.