Investigating the effect of mechanical activation duration (MAD) on the microstructure and corrosion behavior of TiAl intermetallic compounds

An innovative method for fabrication and investigating the effect of mechanical activation duration (MAD) on the properties of TiAl alloys was developed. The study employs an efficient implementation of combustion reactions in a compressed, mechanically activated mixture of titanium and aluminum, leading to the synthesis of titanium aluminide (TiAl). The induction-activated method initiates an exothermic reaction between Ti and Al, facilitating simultaneous preheating and ignition under an argon gas atmosphere. The accomplishment of the synthesis process lasted very short times, and the products were characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) techniques. The investigation focuses on samples with MAD durations ranging from 1 to 10 h, revealing that higher MADs (4 to 10 h) result in an innovative microstructure with α₂ (Ti₃Al)/γ (TiAl) round-shape lamellar grains embedded in the γ (TiAl) matrix. This microstructure enhances the toughness of TiAl alloys while maintaining comparable hardness. The study indicates that increasing MAD from 1 to 10 h improves reaction kinetics, leading to a rise in reaction front velocity from 3.95 to 5.02 mm s⁻¹ and a reduction in α₂ (Ti₃Al)/γ (TiAl) round-shape lamellar grain size from 215.804 to 172.709 μm in a more homogeneous arrangement. Furthermore, corrosion behavior analysis for samples with 1 and 10 h MAD reveals an increase in the resistance of the oxide layer (R_f) value from 702.9 to 43111 Ω.cm² and the charge transfer resistance (R_ct) value from 41.84 to 18520 Ω.cm².