EFFECT OF COOLING RATE ON MICROSTRUCTURE AND PROPERTIES OF Fe₃Al INTERMETALLICS

Fe₃Al intermetallics were solidified separately in sodium silicate sand mould and permanent mould to get different cooling rates. After heat treatment (1000°C/15h homogenizing annealing + furnace cooling + 600°C /1h tempering + oil quenching), the microstructure, mechanical properties and impact fracture of Fe₃Al intermetallics were investigated. The microstructure of Fe₃Al intermetallics is refined and the dispersive second phase is more at higher cooling rate (in permanent mould) than that at lower cooling rate (in sodium silicate sand mould). Compared to intermetallics solidified at lower cooling rate, the Fe₃Al intermetallics solidified at higher cooling rate has the higher tensile strength and good hardness. The impact power increases from 35.28J to 59.09J, while the impact fracture transforms from intercrystalline fracture to intercrystallin+transcrystalline mixed fracture.