High Energy Ball Milling Of Low-temperature Sintering Ultrafine Fe-al Intermetallic Compounds

In recent years there has been considerable interest in the development of iron aluminide corrosion resistant intermetallics. Including Fe₃Al, FeAl, Al₃Fe, for use as high temperature structure materials, properties of high specific strength and high modulus make their being attractive materials within the aerospace industry. Among all the intermetallics, iron aluminide are attractive due to their low material cost and good high temperature mechanical properties. But because of low ductility exhibited at room temperature, and poor machining property etc. the farther application has been limited.Microstructure refinement may improve the mechanical properties of the intermetallics and be discussed in this paper. Firstly high-energy ball milling and mechanical alloying are used to get Fe, Al super-fine powder, and forming through cold pressure. And synthesizing or solidifying FeAl intermetallics by low-temperature sintering. The author has adopted the analysis tech of X radial diffraction to investigate the structure change of mechanical milling powders and done the analysis tech of SEM, to survey the shape and size of them. The author studies the dense process of sintered samples by means of fathoming the dense with the method of excluding water. In addition, microscope structure, reaction process, crystal shape and size of sample are analyzed by adopting the analysis tech including optical microscope, scan electric microscope, X radial diffraction, and AFM. Meanwhile; mechanical property is primarily analyzed by means of fathoming hardness of sample.The Nanosizing mechanism of the milled powder is also discussed.The results shows: Fe (Al) solid solution can be synthesized through mechanical alloying 8h or longer. The average grain size is about 25nm when the Fe₅₀Al₅₀ powder ball milled forl2h, the lattice parameter is 0.2889nm, and the microstructure is Nanosized. For the pressed green compacts with the same milling times, the green density increases with increasing the forming pressure. But for the pressed green compacts with the different milling times, the density performance reduces with increasing the forming pressure, and the indurations become remarkable. The authoradopt solid sintering, increasing the sintering temperature, the powder become easier to sinter, the diffusing reaction between iron and the aluminium has been accelerated. So has the speed of matter. The density and hardness have been increased markedly. It is unconspicuous to increase the keeping time.The result shows that it is very idle to fabricate FeAl nanosized bulk material, whose dense degree is 94 percent, whose crystal size is 30nm and whose hardness is 569(HV), by using the parameter as follows: the parameters of ball milling is that the evolving rate is 60r/min, rate of ball to powders is 40:1, time is 12 hours, Dwell time and forming pressure are determined to be 20s and 250MPa, and the parameters of sintering is that the sintering temperature is 620°C, the sintering time is 4h. SEM photographs of nanometer FeAl intermetallics bending resistance specimen has apparent model nest, which shows that the sample occurs definite model distortion. It shows that the plasticity could be improved by high-energy ball milling.