Mechanical properties of Fe-Al-Ta eutectic composites at higher solidification rates

As is known, solidification rate has an obvious effect on microstructure and property. Mechanical properties of Fe-Al-Ta eutectic composites at the solidification rates of 650 μm/s, 700 μm/s, 800 μm/s and 900 μm/s were studied in the present paper. Microhardness, tensile property and fracture toughness of Fe-Al-Ta eutectic composites at different solidification rates were studied respectively. Microhardness value of directionally solidified Fe-Al-Ta eutectic composites is significantly increased as compared with that of the as-cast alloy, and the relationship between microhardness and lamellar/rod spacing satisfies Hall-Petch Formula. There is no obvious plastic deformation characteristic during the process of tensile loading and the eutectic structure fracture is brittle fracture. In addition, the three-point bending fracture toughness is firstly increased then decreased with the increase of the solidification rate. When the solidification rate gets to 700 μm/s, the fracture model of Fe-Al-Ta eutectic composites is a cleavage-dimple mixed fracture, and the fracture toughness reaches the maximum value. The toughening mechanism can be ascribed to fine grain strengthening, crack deflection and interface enhancement.