Rising crack-growth-resistance behavior of Al_2O_3 based composites toughened with Fe_3Al intermetallic

摘要

Al_2O_3 based composites containing 5-20 vol. percent of Fe_3Al intermetallic second-phase particles were prepared by hot-pressing sintering. Significantly improved fracture toughness (8.1 MPa m~(1/2)) and bend strength (860 MPa) were achieved in Al_2O_3/20 vol. percent Fe_3Al composite. The R-curve behavior for Al_2O_3/5-20 vol. percent Fe_3Al 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 Al_2O_3matrix and Fe_3Al particle.