High Temperature Properties Of Fe-Al-Ta Eutectic Alloy

Fe-Al intermetallic compounds have certain long-range order in their microstructures.Fe-Al intermetallic has advantage on physical properties?such as resistant to high temperature oxidation,thermal corrosion and sulfidation?and mechanical properties?such as specific stiffness and specific strength?as compared to other intermetallic.Its toughness is higher than that of high-temperature ceramic materials but lower than that of nickel-based alloy.Fe-Al-based alloy has a series of advantages such as low density,high impact resistance,high abrasion resistance and low cost,so Fe-Al-based materials have broad development in the structural materials,and it is expected to replace traditional stainless steel,Titanium alloys,nickel-based alloys,etc.However,the application of Fe-Al intermetallic compounds is limited by room temperature brittleness and sharp decrease in strength above 600°C.In this paper,an appropriate amount of Ta element was added to Fe-Al intermetallic and Fe-Al-Ta eutectic composites at the solidification rate range of90?600?m/s were prepared by Bridgman directional solidification technology.The solidification characteristics were studied by SEM,and the interlaminar spacing of Fe-Al-Ta eutectic with different solidification rates was predicted by using the classical theoretical model.The tensile properties and fracture toughness of Fe-Al-Ta eutectic composites at600?were studied by tensile test and three-point bending method.It can be found that its fracture mode is ductile fracture at high temperature,and the tensile strength at high temperature is higher than that at room temperature by analyzing and comparing the fracture morphologies and stress-strain curves.It shows that there is a large number of dimples existed at the fracture of Fe-Al-Ta eutectic composites at 600?,and the size of dimples decreases with the increase of the tensile rate.Fe-Al-Ta eutectic composites was subjected to high temperature oxidation test by constant temperature oxidation.The test temperatures were 600?,700?and 800?,respectively,and the sampling time interval was 20 h.The oxidation weight gain curve of Fe-Al-Ta eutectic is linear.The oxidation weight gain at 800?is significantly higher than that of 700?and 600?.The morphology and phase composition of the oxide layer were analyzed by XRD,SEM and EDS.It shows that the oxide layer was composed of iron oxide at 600?800?.At the beginning,Al₂O₃ was generated,but it is difficult to form a dense oxide film due to less Al.Fe³⁺is gradually spread outward to generate Fe₂O₃ oxide with the increase of time.