INFLUENCE OF SINTERING TEMPERATURE ON THE STRUCTURE AND PROPERTIES OF IRON ALUMINIDE Fe₃Al

Abstract

The paper examines how the heating temperature and isothermal holding time influence the phase composition, structure, and physical and mechanical properties of samples sintered in vacuum from iron aluminide Fe₃Al synthesized from a mixture of iron and aluminum powders. Dilatometric studies show that the preforms change their density in a complex manner in the sintering process. The porosity first increases from 15% in the initial billet to 45% at 950 °C and then decreases to 5% at a sintering temperature of 1450 °C. X-ray diffraction was employed to study the synthesis of intermetallics compounds by heating the powder mixture. Intermetallic compound Fe₂Al₅ forms in an amount within 30% at 600 °C in one-hour isothermal holding. When holding time increases to 3 h or temperature to 950 °C, intermetallic compound FeAl (B2) forms and gradually grows in content. With a further increase in sintering temperature to 1450 °C, the amount of the A2 phase becomes greater, the concen-tration of iron and aluminum of this phase approaches the stoichiometric ratio of Fe₃Al over the entire cross-section. The mechanical properties of iron aluminide increase with sintering temperature but especially distinctly after being sintered at 1450 °C, when planar pores close and perfect contacts between particles form. A sintering temperature of 1450 °C allows the samples to be produced with minimal porosity, uniform distribution of elements, and the best combination of mechanical properties: bending strength 980 MPa and fracture toughness 24.5 MPa • m^0.5. While the strength and fracture toughness increase with sintering temperature, the fracture mechanism changes from intercrystalline to transcrystalline.