Synthesis of Nanostructure Ti-45Al-5Cr Alloy by Mechanical Alloying and Study the Effect of Cr Addition on Microstructure of TiAl Alloy

In this work, mechanical alloying was employed to produce Ti-50Al and Ti-45Al-5Cr (at%) alloys. Alloying was performed in a planetary mill and the alloying time varying from 5 to 70h. Characterization of the powder mixture was performed by X-ray diffraction (XRD), SEM analyses and DTA test, during mechanical alloying and after annealing at 1100°c in vacuum oven. The results showed, after 50h of milling of TiAl powder mixture, only a complete amorphous phase was detected but with Cr addition (5at%) the Cr (Ti,Al) solid solution within the amorphous matrix were identified. After annealed of mechanically alloyed Ti-50Al for 50h, the γ-phase with high purity and nanostructured size was produced but for sample with Cr addition, TiAl(γ) and amount of Ti3Al(alpha2) were detected. Cr accelerated the production of duplex structure (gamma+alpha2). It suggested the Cr(Ti,Al) solid solution was dissolved in TiAl(gamma) and Ti3Al(alpha2).