Fatigue and fracture toughness of Fe3Al alloys with additions of Zr and C

Fracture behaviour of two intermetallic alloys based on Fe3Al with different Zr content was studied. On the alloy Fe-29.5Al-2.3Cr-0.63Zr-0.2C (at.%) (FA06Z), basic characterization of the microstructure by light and electron metallography was carried out. Tensile tests and fracture toughness tests were performed at 20, 200, 400, and 600 degrees C. The values of fracture toughness vary from 26 MPa m(1/2) (at 20 degrees C) to 42 MPa m(1/2) (at 400 degrees C). The fractographic analysis showed that the samples fractured at 20, 200 and 400 degrees C in the tensile or fracture toughness tests exhibit transgranular cleavage fracture, while the ductile dimple fracture predominates at 600 degrees C. Previous fatigue experiments on the alloy Fe-31.5Al-3.5Cr-0.25Zr-0.2C (at.%) (FA02Z) were completed by fatigue tests at 150 and 600 degrees C. The highest fatigue life and the lowest fatigue crack growth rates were found at 150 degrees C. The fatigue samples tested at all temperatures (20 to 600 degrees C) failed by transgranular cleavage fracture.