Rising crack-growth-resistance behavior of Al2O3 based composites toughened with Fe3Al intermetallic

Al2O3 based composites containing 5–20 vol.% of Fe3Al intermetallic second-phase particles were prepared by hot-pressing sintering. Significantly improved fracture toughness (8.1 MPa m1/2) and bend strength (860 MPa) were achieved in Al2O3/20 vol.% Fe3Al composite. The R-curve behavior for Al2O3/5–20 vol.% Fe3Al composites was estimated by the indentation-strength method. The quantitative analysis of toughness increment indicates that the improvement was attributed to the crack bridging and residual thermal stress toughening effect. High-resolution transmission electron microscopy (HREM) shows that no micro-crack was observed at the interface due to the small thermal expansion coefficient mismatch, and no reaction phase existed at the interface between Al2O3 matrix and Fe3Al particle.